Franklin D. Roosevelt, ‘Gray Zone’ Warrior


In 2014, Russia’s invasion of the Crimea was famously characterized by “little green men'”taking control of key Ukrainian infrastructure, disrupting Ukrainian communications, and in some cases trying to get Ukrainian troops to switch to Russian allegiance. In the South China Sea, China has been accused of claiming sections of international waters as extensions of its own territory and occupying and fortifying uninhabited islands as it would sovereign territory. Both nations engage in a process known as “salami slicing,” gradually pushing the limits of the boundary between war and peace to achieve potentially warlike national objectives short of conducting actual hostilities. These examples constitute ‘gray zone warfare,’ defined by a 2015 U.S. Special Operations Command White Paper as “competitive interactions among and within state and non-state actors that fall between the traditional war and peace duality.”

While analysts tend to view gray zone warfare as a modern innovation, a departure from an older and more traditional form of waging war, it was in fact readily familiar to previous generations. President Franklin D. Roosevelt was an active and enthusiastic practitioner of the art of gray zone warfare in the period just before the Japanese attack on Pearl Harbor, when the United States was not yet officially a belligerent in World War II.  Roosevelt used the Navy, Marines, and the Coast Guard to drive German naval forces from the western Atlantic Ocean, secure the overseas possessions of Allied nations conquered or menaced by the Nazi regime, and provide material aid to the Allied cause. All of these goals were accomplished short of actual war. Roosevelt’s “little gray ships” effort is a good example of how a nation can aggressively use conventional seapower short of war to achieve its strategic ends.

What is Gray Zone Warfare?

Former NATO Supreme Commander Admiral James Stavridis further defined gray zone warfare in the naval context as “maritime hybrid warfare” in which sailors without uniforms might operate warships disguised as merchant vessels and conduct warlike acts without attribution. One example of such activity from the age of fighting sail was the privateer;: A civilian ship with a civilian crew authorized to conduct warlike actions by a nation perhaps not interested in being directly linked to those missions. Another example cited by Stavridis was the “Q-ship” of World War 1, which was a merchant ship armed with naval weapons and manned by a naval crew with the mission of luring complacent submarines seeking an easy victory into the range of its guns. Both of these examples informed Roosevelt’s thinking as he looked for ways to counter the growing naval power of Nazi Germany in the late 1930s.

FDR and the Gray Zone

Like Winston Churchill, Roosevelt recognized the aggressive and duplicitous nature of the Nazi regime and was determined to prepare and protect U.S. strategic interests in case of eventual war with Germany. Once war broke out in 1939, the president sought to aid Great Britain, France, the Soviet Union, and other states fighting Nazi Germany and fascist Italy. Given the antiwar, isolationist stance of the majority of the U.S. population in the mid to late 1930s, Roosevelt knew that unconventional measures might be needed.

His chief tool in this enterprise was the U.S. Navy. The president had been assistant secretary of the Navy from 1913 to 1920, and had an idea for how the sea service could be used to aid the Allies and to thwart German plans to sever the Atlantic sea lines of communication without actually going to war with Germany. He was also a fan of naval history , and turned to the past in search of methods to counter German activities. The president likened his aggressive attempts to oppose German naval activities in the Atlantic to the 1798-1800 “Quasi-War,” in which famous U.S. Navy warships such as the frigates USS Constitution and USS Constellation battled French Republic privateers while the United States remained officially neutral.

Roosevelt’s first task was to keep the Germans out of the Western Hemisphere. After the 1938 Munich Agreement failed to curb German aggression to its east, Roosevelt determined to create a Neutrality Zone in the Western Hemisphere patrolled by U.S. warships that would enforce the right of free navigation, report on the positions of German merchant ships and warships, and actively aid Britain and France in locating them. Upon the outbreak of war in September 1939, Roosevelt declared a 200 to 300-nautical-mile deep Neutrality Zone in the Atlantic adjacent to the North and South American continents. He got the Organization of American States, and most importantly, an isolationist Congress, to agree to his actions and give them domestic and international legitimacy. Most U.S. naval strength was based in the Pacific to counter the imperial ambitions of Japan, but Roosevelt transferred some ships to the much weaker Atlantic Squadron, brought older ships out of retirement to join the new neutrality patrol in the Atlantic, and appointed the mercurial and aggressive Admiral Ernest King as its leader. The new “Atlantic Fleet” would be the main tool in Roosevelt’s gray-zone effort to deter the Germans and perhaps bait them into an active war.

Roosevelt correctly assessed that Hitler would be compelled to avoid war with the United States so that he would not have to face a transatlantic enemy while finishing his war with Britain and preparing for an all-out conflict with the Soviet Union. The Germans began the war by deploying limited groups of submarines to positions west of Iceland, but outside Roosevelt’s declared neutrality zone.  German ships were ordered to wage war based on a set of rules developed during the 1930 and 1936 London Naval Treaty Conferences where submarines had to surface and identify a merchant as hostile, and allow its crew to evacuate before sinking the ship. Warships and troopships were exempt and could be sunk from a submerged position without warning. When the German submarine U-39 sank the British passenger ship Athenia, (mistaking it for a merchant cruiser) Hitler further tightened the rules by forbidding all attacks on passenger ships, even those in convoys.  The Führer specifically ordered his submarine commander Admiral Karl Dönitz to keep his submarines east of Newfoundland and specifically to avoid any attacks on U.S. ships.  Dönitz later interpreted Hitler’s orders as a ploy to keep alive the option of a negotiated peace with Britain and prevent a repeat of World War I, when the U.S. entered the war after German submarine attacks on its ships. Hitler’s insistence on avoiding conflict with the United States enabled Roosevelt to further expand what the Navy could do to combat German efforts in the North Atlantic. One historian later referred to “the Atlantic Fleet’s private war against the Germans.”

Germany’s defeat of France in May 1940 forced Roosevelt to step up the pace of his efforts to aid Britain and actively combat the Germans, while still keeping the United States out of the war.  In August of that year, Roosevelt transferred 50 overage destroyers to the British to support Atlantic convoy escort in return for 99-year leases on British bases in Newfoundland and the Caribbean. After the Germans conquered Denmark in April 1940, Roosevelt dispatched U.S. Coast Guard cutters to Greenland to ensure that the Danish possession did not fall under German control. Coast Guardsmen supplied Greenlanders with weapons and reported on German attempts to create a weather station on the island. The Coast Guard provided the station’s location to the Allies and it was destroyed by a Norwegian gunboat. The Coast Guard even left a coastal defense gun manned by a U.S. Coast Guard landing party in place to defend against future German incursions. The United States finally declared Greenland a U.S. protectorate in 1941.

Supplying the British with essentially free warships was not necessarily gray zone warfare. However, since the Americans and the British now operated the same classes of destroyer in active Atlantic operations, confusion between active combatant and neutral was inevitable and would play a role in the later sinking of USS Reuben James. Taking possession of a combatant (Denmark’s) territory, and enabling its inhabitants to conduct combat operations, however, would seem to pass the gray zone warfare test.

Roosevelt’s efforts increasingly went beyond material support and securing key Atlantic geography as the war continued. He committed the Navy to active support of the Western Allies. U.S. ships aggressively reported the positions of the few German civilian ships remaining in the Western Hemisphere and actively helped the British capture them. Roosevelt ordered the award-winning German passenger liner Bremen detained for an extended period in New York to give the British time to dispatch ships to capture her. While Bremen eventually was allowed to leave and evaded her British pursuers in coastal New England fog banks, the German liner Columbus was not so lucky. Several U.S. Neutrality Patrol ships shadowed the ship for several days and broadcast her position to British ships, which later confronted the liner and demanded her surrender. The Germans scuttled the ship, and U.S. sailors rescued the crew. The U.S. government ordered all log book references to the broadcasting of the position of the Columbus removed from the record. Roosevelt’s selective reporting of German ships seems to have been effective, as only 32 of the 85 German merchant ships in the Western Hemisphere at the outbreak of war in 1939 found their way home. In comparison, 100 of the 126 German merchant ships in other parts of the world in September 1939 managed to return unscathed to Germany. While overseas commerce and North Atlantic passenger service were not significant parts of the German war effort, the ships involved in those trades represented a significant amount of German commercial and state property. The United States actively assisted the Allies in depriving Germany of those assets before entering the war, another example of gray zone operations.

Finally, and most importantly, the president authorized the Navy to actively protect the convoys carrying material aid to Great Britain. U.S. destroyers began escorting British Atlantic convoys from ports in North America to the boundary of the U.S.-declared Neutrality Zone and actively cooperated with British counterparts in the detection of and combat against German submarines. The May 1941 British capture of a working German Ultra cryptographic machine allowed the two future Allies access to detailed German submarine communications and locations.

The ‘Quasi War’ Escalates

These missions were not without significant risk. Tired and frustrated German submarine commanders began to engage U.S. warships in active combat despite orders to the contrary from Hitler and Dönitz. In June 1941, the German submarine U-203 tracked and nearly torpedoed the U.S. battleship Texas when the submarine’s commander believed the U.S. battlewagon was operating in the declared German war zone. On Sept. 4, 1941, the destroyer USS Greer was fired upon by the German submarine U-652 while working with a British Hudson antisubmarine plane to detect and sink the German vessel. Roosevelt condemned the Germans for the attack and, one week later, used it as a pretext to declare all German and Italian warships within the U.S. Neutrality Zone to be hostile ships subject to U.S. defensive measures. The Germans were so concerned that Hitler limited German submarine attacks to only large warships that were clearly identified as hostile units for the next several weeks and avoided attacks or even active defense against the destroyers and other escort ships most capable of sinking a submarine.

The United States Marine Corps joined Roosevelt’s Atlantic gray zone campaign in July 1941 when it formally relieved the British of the occupation of the strategic, mid-Atlantic island of Iceland. Churchill had occupied Iceland with British forces the year before, saying, “Whoever possesses Iceland holds a pistol firmly pointed at England, America, and Canada.” The Marines were given an ominous general order: “In cooperation with the British Garrison, Defend Iceland against Hostile Attack.” The Marines did not see active combat in Iceland, and did not hide their identity as did the Russian soldiers participating in the modern-day Ukrainian conflict. Still, their direct cooperation with British forces in preparation for repelling a German attack resembles gray zone warfare.

While the “little green Marines” were securing Iceland, the undeclared naval war in the Atlantic entered a more violent phase that for the first time included direct combat against German naval forces, even while the United States was still officially at peace with the Third Reich. On Oct. 17, 1941, another convoy escort, the destroyer USS Kearny, and several other U.S. warships responded to distress calls from Canadian convoy escorts requesting aid in stopping a submarine attack. The U.S. ships dropped depth charges on suspected submarine targets, and German submarines returned fire, hitting Kearny with a torpedo and killing 11 U.S. sailors. On Oct. 30, the destroyer USS Reuben James, escorting another convoy, attempted to engage a submarine contact with depth charges. Early the next morning, the Reuben James was sunk by a torpedo fired by the German submarine U-552, with 100 U.S. sailors lost. While public outrage soared and folk singer Woody Guthrie wrote a song praising the lost sailors from “the good Reuben James,” the United States remained at peace with the Nazi state. Chief of Naval Operations Admiral Harold Stark wrote, “The Navy is already at war in the Atlantic, but the country does not seem to realize it. Apathy to the point of open opposition is evident in a considerable section of the press. Whether the country knows it or not we are at war.”

U.S. warships continued this undeclared war against German submarines right up until Germany declared war against the United States on Dec. 10, 1941, in support of its Japanese ally’s attack on Pearl Harbor. Hitler had the option of remaining neutral, as Japan had not itself been attacked, but perhaps finally exhausted by Roosevelt’s undeclared naval war, he decided to commit Germany to general war with the United States. This fatal decision would play a significant role in bringing about Germany’s final defeat by the Allied powers in May 1945.


Gray zone warfare did not end with World War II. Roosevelt’s strategy and the tactics he used to achieve them are similar to modern-day efforts to achieve goals short of actual war. For instance, Roosevelt’s unilateral declaration of U.S. control over other nations’ territories and international waters, and his use of the Coast Guard units for combat purposes, are echoed in China’s efforts today to declare the South China Sea as Chinese waters and its use of Maritime Militia units to harass non-Chinese ships in waters Beijing wishes to control. Roosevelt used U.S. warships as active combat participants in convoy operations when the country was officially at peace, just like Russian naval forces conducted geographically-discrete combat operations against both Georgian and Ukrainian navies to further Russian political goals in the undeclared wars there. Russian naval forces engaged and sank Georgian patrol craft that ventured into self-declared Russian exclusion areas similar to U.S. destroyer operations against German U-boats in Roosevelt’s Maritime Exclusion Zone.

The United States has in the past displayed considerable prowess in naval gray zone warfare, and can do so again. It is not a tool that should be ceded to current competitors such as Russia and China. The wide history of U.S. naval gray zone warfare, from the Quasi-War with France to more recent examples, including the Naval Quarantine of Cuba in the 1962 Cuban Missile Crisis and the 1987-1988 Tanker War in the Persian Gulf, should be prime reading material for those seeking ideas to counter Chinese and Russian maritime gray zone efforts.


Steven Wills is an analyst at CNA, a research organization in Arlington, VA, and an expert in U.S. Navy strategy and policy. He is a Ph.D. military historian from Ohio University and a retired surface warfare officer.

The views expressed in this article are those of the author and do not necessarily reflect the views of CNA or any of its sponsors.

Image: National Archives