Urban Warfare, Sieges, and Israel’s Looming Invasion of Gaza

With Israel’s looming ground offensive against Hamas, and considering the population density of Gaza, urban warfare will certainly be a significant component of the conflict. Urban warfare in Gaza will not be a deft war of maneuver, but rather a slow, methodical grind of attrition. The Israel Defense Forces’ relatively small size in relation to the population density and urban sprawl of Gaza will strip away many of the Israeli military’s inherent asymmetries. Moreover, two additional factors will increase the voracity of urban warfare. First, due to Gaza’s small size, there is almost no land available to fight a war of maneuver on open, flanking terrain. Second, even if there were available open terrain, Hamas will benefit from fighting within the tight confines of the city, whereas the Israel Defense Forces are optimized for mobile warfare on barren plains. As a result, outsiders must anticipate that the conflict will be urban, and because Hamas fighters will not willfully expose themselves to the Israeli military’s sophisticated weaponry, I believe Hamas fighters will hug both Gaza’s urban infrastructure and nest within its civilian population. By staying close to infrastructure, Hamas’ fighters are afforded basic protection from the Israel Defense Forces’ ability to observe, detect, and precisely target their force. At the same time, by operating amongst the Gazans, Hamas can capitalize on the brutality of urban warfare in the information spectrum by showing the world the death and destruction that accompany combat in urban areas. 

The siege is a critical component of urban warfare, yet it is often overlooked in today’s analysis of armed conflict. The reasons for this are varied, but more than likely this has to do with the term itself. The word siege immediately elicits images of trebuchets, ballistas, and castles on 16th-century European battlefields. Nevertheless, in recent years a handful of scholars stepped into the murky waters of sieges to better understand how they fit into contemporary armed conflict. Drawing on observations from wars in Syria, Iraq, Ukraine, and the Philippines, for instance, Harvard Law School, in coordination with the International Committee of the Red Cross and the United States Military Academy’s Lieber Institute, hosted a two-day conference in the spring of 2022 on international law applicable to sieges in urban warfare.   

Moreover, Professor Anthony King also examined sieges in his work Urban Warfare in the Twenty-First Century. King situates sieges in their modern military and geopolitical context, arguing that the increasing size of cities, coupled with the decreasing size of militaries, finds micro-sieges becoming a common occurrence in armed conflict. Small contemporary forces use micro-sieges, as opposed to full-scale sieges, to isolate only one part of a much larger urban area, to maximize the siege’s effect on the military force and civilian population trapped therein. Operation Iraqi Freedom’s battle of Sadr City is one example of a micro-siege, whereas the Russo-Ukrainian War’s siege of Donetsk Airport (also referred to as the Second Battle of Donetsk Airport) is another classic example of a micro-siege.     

Sieges, however, are neither an anomaly of contemporary armed conflict, nor something that is the result of bad tactics or attritionalist ways of warfare. A survey of armed conflict finds that 60 sieges of various sizes and duration have accompanied conflict since the end of the Cold War. Moreover, all 60 of those sieges occurred in urban areas. Given that arc, and the likelihood that urban warfare will play a significant part in the Israel Defense Forces’ Gaza offensive, it is not a stretch to assume that sieges will maintain a central position within the looming conflict. The international community should thus expect to see one, if not more, sieges during the ground offensive. Given the Israel Defense Forces’ size relative to Gaza’s urban population, these sieges will likely be proximal micro-sieges, radiating from Israeli bases of power and oriented on tactical and operationally relevant military, and potentially political, objectives. Based on quantitative analysis of post–Cold War sieges, if Israel can conduct its sieges between one to 12 months, then they will be operating in the space in which states most often win sieges. Regardless, sieges, much like the other facets of urban warfare, are dirty, deadly business. Israel will have to balance the purpose and effectiveness of siege operations against the international community’s response to identify the true impact of those operations.  

What Are Sieges?

Sieges are a multifaceted tool for combatants in armed conflict. Sieges are typically associated with an aggressor encircling a defender. The defender is historically a military force, but by virtue of that force being entrapped in an urban area, noncombatants come under siege as well. This is now the case in Gaza. Aggressors can be any actor — state, non-state actor, proxy force, mercenary group, or any other combatant with the strength to snare an adversary in a city or town. 

Encirclement, however, is not a siege’s causal mechanism. In some cases, an aggressor does not possess sufficient size to entirely encircle an urban area, but still finds value in prosecuting a siege. Therefore, the aggressor knowingly executes a porous siege. Operation Inherent Resolve’s siege of Mosul (2016–17) is an example of this situation. The Iraqi Security Forces, bolstered by the U.S.-led coalition to defeat the Islamic State of Iraq and the Levant, did not possess sufficient force to completely encircle the city of Mosul. The Iraqi Security Forces and U.S.-led coalition nonetheless bifurcated the city and conducted micro-sieges to squeeze the life out of the Islamic State. In many other cases, however, adroit actors will leave a portion of a siege open. The aggressor might do this for a variety of reasons. 

First, a porous siege provides the aggressor with intelligence. An open artery to and from a siege affords an aggressor the opportunity to observe what goes into and comes out of a besieged area. That information, in turn, allows an aggressor the opportunity to better understand the defender’s capabilities, resource capacity, and force disposition.    

Second, an aggressor might use a siege as a punitive action. Consequently, leaving a valve open allows the aggressor to keep metered amounts of supply flow into a besieged area, allowing the defending force and the affected population to remain in the fight longer than they would if contact with the outside world were cut entirely. In doing so, the aggressor can actually increase the severity of punishment on the besieged actor by applying a steady degree of death and destruction on the defender over time. The sieges at Donetsk Airport (2014–15) and Mariupol (2022) are examples of this dynamic. In each case, had the Russian military and its proxy forces closed the perimeters entirely, the Ukrainians would have likely faltered much sooner. But having left a small artery open, the Russian military and its proxy forces inflicted greater punishment by extending the time in which they made Kyiv’s forces defend themselves and spend resources to sustain their force.     

Third, a porous siege allows a cynical aggressor the ability to provide a nod of nominal good will to the international community and the provisions of international humanitarian law. Yet, similar to the first option, this also provides an aggressor the opportunity to gain information on the status of the defender’s forces, the overall situation, and force locations.  

If an encirclement is not a siege’s causal mechanism, then what is? Put simply, actors use sieges because they accelerate an adversary toward exhaustion and, as Professor Cathal Nolan writes, exhaustion through attrition is how wars are won and lost. Exhaustion is the materiel inability and/or cognitive unwillingness of an actor to continue fighting. Sieges, unlike head-to-head battles, are one of the best ways an actor can effectively impose materiel loss on their adversary, while parrying the reciprocal loss.      

It is important to note that a siege is not just a tactical consideration. Sieges can occur in battles, but in most cases, sieges are more often operational and strategic military activities. Time is a useful independent variable for categorizing sieges into tactical, operation, and strategic consideration. Time is a good metric because it reflects the tension between resource consumption, resupply, operational and strategic resources, and resource distribution across all levels of military activity. Put another way, time is a useful metric because it closely links military activities with exhaustion. 

Carrying this idea forward, it is possible to categorize sieges of 30 days or less as battles, sieges of a month to six months in length as operations, and any siege longer than six months as a campaign. Referring back to the 60 post–Cold War sieges referenced earlier in this article provides interesting results. Tactical sieges (i.e., battles) occurred in 18 percent of the cases. Operational level sieges, or those lasting from six months to a year, occurred 35 percent of the time. Strategic sieges, or those lasting longer than a year, account for 47 percent of the post–Cold War sieges. Of that 47 percent, 18 of those sieges lasted significantly longer than a year. Given the data, despite the lack of acknowledgment in many policy, academic, or defense circles, sieges are considerably more important than mere tactical considerations.    

Who Wins?     

In building my dataset on sieges, I began with the post–Cold War period because it more closely aligns with today’s state of the international system than does examining the problem from an earlier point in history. This is important because war and warfare often reflect the periods of time in which they originate. Therefore, data about a modern siege, for instance, would be skewed by incorporating siege information from a period such as World War I or the 19th- century Crimean War. 

My research combed through armed conflict in the post–Cold War period and identified 60 sieges. I found that sieges occurred in almost every conflict from the Yugoslav wars of the early 1990s to today’s conflicts in Mali and Sudan. Through my research, I sought to find answers to the following questions: Does the aggressor or defender most often win in a siege? Using states, non-state actors, and principal-proxy dyads as the metric for measurement, which actor fairs better in sieges? What factor does time play in sieges?

As is explained below, I found that aggressors do win more often than defenders in a siege. However, they do not win as unanimously as one might think. Second, non-proxy aligned states come out on top in most sieges, with proxy dyads coming in second, and non-proxy aligned non-state actors finishing last. Regarding time, proxy dyads and non-state actors prevail 80 percent of the time in sieges lasting 30 days or less. States, on the other hand, come out on top 52 percent of the time in sieges lasting between one and six months, and they win 82 percent of the time in sieges that go on for six months to one year. Surprisingly, sieges lasting longer than a year see the state’s dominance give way. States prevail in 39 percent of sieges lasting longer than a year, whereas non-state actors prevail 28 percent of the time, followed by proxy dyads at 17 percent. Although I do not have the data to explain why states thrive in the middle of the siege timeline continuum and do not thrive on the short and long ends of the spectrum, the assumption is that the middle band — between one month and one year — better suits a state’s logistics network. On the short end of less than a month, states might not perform as well because they are quickly overcome by surprise. On the long end of the spectrum, or longer than a year, a state’s power might wain due to flagging political or domestic support. Nonetheless, further research is required to make better educated insights to that problem.    

 
Having framed sieges in post–Cold War armed conflict, who most often wins in siege situations? Of the 60 sieges recorded between the end of the Cold War and today, 60 percent have been won by the aggressor, 30 percent by the defender, and the remainder split between ceasefires, multiple victors, and stalemates, with a few that are ongoing. The besieging actor — referred to as the aggressor — is commonly (61 percent), but not always, a state. Non-state actors, on the other hand, are the aggressor 34 percent of the time. The remaining 5 percent is split across other non-traditional combatants such as proto-states and principal-proxy dyads.

Based on the type of actor, what do the statistics say regarding war outcomes? States win sieges 48 percent of the time. Of significant importance, principal-proxy dyads come in second in win percentage. Principal-proxy dyads, such as Russia and the Donetsk People’s Army, for example, come out on top 23 percent of the time. Non-state actors follow principal-proxy dyads, registering victory 18 percent of the time. The remaining percentage is split amongst stalemates, ceasefires, and ongoing sieges.   

The data thus indicates that the aggressor, regardless of their status as a state or non-state actor, is likely to win a siege. Nevertheless, the defender’s 30 percent win percentage suggests an aggressor’s success in entering into a siege is anything but a foregone conclusion. If Israel initiates a siege or series of sieges in Gaza, it is statistically acceptable to assume an Israeli victory. Yet at the same time, if Hamas enlists proxies, or if it operates as a proxy for a larger state such as Iran, it is quite likely that they significantly increase their odds of victory. 

Data aside, the competing strategies of Israel and Hamas, on a tight battlefield spotted with densely populated cities, suggests that a horrific war of attrition is afoot. Moreover, the war of attrition will not be limited to military forces, but it will also consume civilian life. 

The Legality of Sieges

Under the protection of international humanitarian law, militaries are afforded a surprising amount of latitude for siege operations. Under international humanitarian law, military necessity, proportionality, and distinction are what provide commanders the legal freedom to conduct sieges. Article 23(g) of the Hague Convention of 1899/1907 outlines what is acceptable under the principle of military necessity. Article 23(g) states that a combatant is prohibited from destroying or seizing an adversary’s property, unless the destruction or seizure of property is demanded by the necessities of war. Moreover, this principle must be applied in consideration of other elements of international humanitarian law. Further, military necessity does not act as a defense for prohibited acts. 

Proportionality, on the other hand, states that the loss of life and destruction of property that accompany an attack must not be excessive considering the tangible military advantage expected to be gained.  

Distinction is the most important element of international humanitarian law relating to sieges. Additional Protocol I prohibits indiscriminate attacks. The protocol’s Article 51 outlines the protection of civilian populations in war zones. Article 51 states that civilian populations and individual civilians should be protected against the inherent dangers of war. Moreover, civilian populations and individual citizens should not be the object of military attacks. Further, attacks or threats of violence to terrorize the civilian population or individual citizens are prohibited. Importantly, Article 51 also makes provisions for civilian populations or individual citizens who take it upon themselves to take up arms. It asserts that once an individual or group of individuals directly participates in hostilities, they lose their protected status.    

Further, distinction is important when considering sieges because of the likelihood of indiscriminate attacks. Article 51 provides three provisions defining indiscriminate attacks: attacks not directed at a military objective, attacks using a method or means that cannot be directed at a specific military objective, and attacks whose method or means cannot be limited to a military objective. In addition, Article 51 records two types of attacks that are categorically defined as indiscriminate and thus violate the principle of distinction. Those two conditions are: a bombardment that treats a city with multiple military objectives within it as one collective military objective, and an attack that generates loss of civilian life, injury to noncombatants, and destruction of civilian infrastructure that is excessive to the military objectives.  

Additional Protocol I, Article 51 also asserts that reprisals against civilian populations, individual civilians, and civilian objects are prohibited. Military forces are not allowed to move civilian populations or forces from one place to another on a battlefield to shield the force from the effects of combat. Put another way, the use of civilian populations and individual citizens as human shields is prohibited.   

Additional Protocol II, among other things, states that combatants must protect civilian populations and that civilian populations and individual civilians must not be the object of an attack. Starvation of civilians is also prohibited as a result of Additional Protocol II. Although it prohibits the starvation of civilians, it does not explicitly state that the starvation of military forces is a violation of international humanitarian law. Regarding starvation, Additional Protocol II also states that the destruction of objects indispensable to the survival of civilian populations, such as food, water, crops, livestock, farming area, and irrigation implements, is strictly prohibited. Note that military forces are again excluded from this condition. 

There are several other agreements that also govern international humanitarian law. The Geneva Convention provides several other distinctions pertinent to the legality of sieges. Moreover, the Rome Statute of the International Criminal Court further codifies many of the provisions found within Additional Protocols I and II, as well as the Geneva Conventions, into a coherent body of rules regarding international humanitarian law. 

The language within the corpus of international humanitarian law is broad and resultantly provides military commanders and their political leadership with latitude to conduct sieges so long as civilian populations are properly accounted for. The language within international humanitarian law selectively excludes military forces as a protected element on the battlefield, thus making operations such as a siege legal under international humanitarian law as it pertains to international armed conflict and non-international armed conflict. 

Moreover, international humanitarian law does prohibit starvation as a method of warfare, but it does not equate sieges with starvation. As a result, sieges in warfare are allowed, so long as the combatants account for and provide protection for the civilian population and individual civilians within the conflict’s zone of military operations. 

The state of Israel, however, is not a signatory to either Additional Protocol I or Additional Protocol II. Israel’s justification for this is that they do not reflect customary law and therefore are not binding. Nonetheless, the Additional Protocols are considered to be norms of customary international law, and they are therefore binding on all parties in conflict, regardless of their status as a signatory or not.

Nonetheless, as several members of the international community, to include the United States, France, Canada, Germany, Italy, and the United Kingdom, recently stated, Israel is well within the parameters of international law to defend itself against terrorism and further terrorist attacks. Israel does appear to be honoring the letter of the law as it pertains to international humanitarian law. It has made several calls for civilian populations and individual citizens to temporarily vacate known hotspots in Gaza. Questions remain, however, regarding the legality of such moves because the mass deportation of groups of individuals can be construed as excessive and not proportional to the engagement area in which Israel intends to operate. Further, Israel is allowing humanitarian aid to reach the Palestinians within Gaza. 

Israel will make mistakes and unintentionally hurt innocent civilians. That is certainly one of the most unfortunate aspects of armed conflict. Nevertheless, Israel and the Israel Defense Forces appear to be judiciously applying combat power against military targets, while adhering to the tenets of international humanitarian law. To address concerns of potential bias, it must be noted that adhering to international humanitarian law does not mean that civilian casualties and collateral damage will not be a byproduct of Israel’s right to defend itself. Moreover, the language used in international humanitarian law is occasionally contradictory and worded so theoretically that it can be used to justify the actions of, or to castigate, any combatant engaged in a conflict. Civilian casualties and collateral damage are an unfortunate part of war, regardless of how closely all parties in a conflict try to adhere to international humanitarian law.     

Conclusion

Given the latitude that international humanitarian law provides states and militaries to conduct a range of military operations, the frequency of sieges in modern armed conflict, and the siege-friendly conditions of Gaza, it is safe to assume that if Israel does initiate a large-scale invasion of Gaza, then sieges will be a key part of the offensive. Moreover, if Hamas does go underground and utilizes the reported tunnel network that links the disparate parts of Gaza with one another, sieges will likely play an important part in countering the tunnel challenge. 

Further, many militaries consider sieges within the acceptable methods of warfare, with the caveat that the civilian population and individual civilians are appropriately protected. Israel, for example, states that sieges are wholly acceptable so long as civilian populations are allowed to leave the city. In terms of process, the onlooker might expect to see a general siege of Gaza, albeit one that is quite porous. Israel will attempt to close routes into the strip, while controlling the flow of humanitarian aid and other necessities of life. Once Israel and the Israel Defense Forces have identified their supporting military objectives, most likely oriented on a city, a garrison, or a force within a city, they will move to establish a micro-siege, or a proximal encirclement and offensive operation against that objective. Due to the considerable force and logistics requirements to maintain a single siege, much less multiple sieges, the Israelis will likely collapse the larger siege of Gaza so to focus forces and resources into micro-siege. Depending on circumstances, the Israelis might keep a small portion of the larger siege of Gaza in place if doing so denies support or reinforcement from external actors.  

Therefore, the international community should prepare itself for the worst. Unfortunately, protections for civilian populations, individual civilians, civilian objects, and resources often fall well short of ideal once hostilities begin. As a result, civilians get caught in the middle of horrible, hostile action between competing parties. Given Gaza’s small size, civilian populations and individual civilians have very little recourse regarding relocating from battlefields. If Israel’s offensive attacks into Gaza with full force, onlookers must thus anticipate significant numbers of civilian casualties and damage to civilian infrastructure. Precision munitions will not provide much assistance in offsetting the problem of civilian casualties and collateral damage. The promise of precision becomes quickly neutralized when operating in dense urban terrain. 

Sieges will likely accompany any Israel offensive into Gaza that looks to gain physical control of territory. Sieges will likely accelerate military casualties, civilian deaths, and damage to civilian infrastructure. Below the surface, sieges will complicate things such as civilian, noncombatant medical care and access to food stuffs and water within Gaza. The international community, to include nongovernment organizations focused on caring for noncombatants in war zones, should proactively prepare for what might well be inevitable and not wait until it is too late, and they are forced to play catch-up. 

Amos Fox is a PhD candidate at the University of Reading. He is currently the chief human resources officer for the Irregular Warfare Initiative and hosts the Revolution in Military Affairs podcast.   

Image: Israeli Defense Forces