In military terminology, a two-front war is a war in which fighting takes place on two geographically separate fronts. It is usually executed by two or more separate forces simultaneously or nearly simultaneously, in the hope that their opponent will be forced to split their fighting force to deal with both threats, therefore reducing their odds of success. Where one of the contending forces is surrounded, the fronts are called interior lines.
The term is also used metaphorically, for example when a moderate ethical, scientific, social, religious or political idea or position is simultaneously being opposed by those to the left and to the right. The popular domestic civil rights and anti-war movement and the contrasting military reality that US combat troops were increasingly exposed to during the late Vietnam War, has also been described as a two-front war.
One of the earliest examples of a two-front war occurred in the third century BC, when the Roman Republic fought the First Macedonian War contemporaneously with the Second Punic War against Carthage. Also, after the consolidation of the Roman Empire's frontier in the reign of Augustus, the Roman forces had to contend with multiple enemies in its frontiers: in the Rhine, Danube and Mesopotamia, with various examples of emperors (such as Septimius Severus and Aurelian) who marched their armies from one side of the empire to another to face them. In the later period, after the collapse of the Western Roman Empire, the surviving part, the Byzantine Empire had to face invaders coming from both west and east and simultaneously trying to preserve its territories in Italy.
Seven Years' War
During the Napoleonic Wars, France repeatedly fought on multiple fronts. For example, France fought the Spanish and Anglo-Portuguese army in the Peninsular War while fighting the Russian Empire at the same time during its invasion of Russia. Their main adversaries the British were also engaged on multiple fronts at various times, having also to contend with the United States starting with the War of 1812 in Canada, the Chesapeake Bay, and Louisiana.
World War I
During World War I, the German Empire under Kaiser Wilhelm II fought a two-front war against French, British, Belgian, and later also American forces on the Western Front while simultaneously fighting the Russians on the Eastern Front. Russian participation in the war ended when the Bolshevik leaders signed the Treaty of Brest-Litovsk with Germany in March 1918. Germany had foreseen such a scenario, and developed the Schlieffen Plan in order to counteract being surrounded by its enemies. Under the Schlieffen Plan, German forces would invade France via Belgium, Luxembourg, and the Netherlands (the idea to go through the Netherlands was abandoned because of the country's neutrality), quickly capturing Paris and forcing France to sue for peace. The Germans would then turn their attention to the East before the Russian army could mobilize massive forces. Due to several factors however, the Germans failed to achieve the plan's aims.
World War II
Perhaps the most famous example of a two-front war was the European theatre during World War II, when Nazi Germany had to confront the Western Allies on the west and the Soviet Union to the east. The Germans were unable to repel either of the advances on the two fronts and eventually lost the war. While there were other contributing factors, such as the insufficiency of the Wehrmacht for a long war and the abandonment of blitzkrieg tactics because of fuel shortages and an increasing need to defend territory, the two-front war was an important factor in deciding when the German military would be forced to surrender.
The Allies, especially the United States, also fought a two-front war, splitting their forces between the European theatre against Nazi Germany and the Pacific War against the Japanese Empire, which was fighting in both Asia and the Pacific.
The Axis Powers had the opportunity to force the Soviet Union into a two-front war by means of a Japanese attack on the Soviet Far East, but the Japanese decided against doing so because of their defeats in the Soviet–Japanese border conflicts. While Germany and the United States remained respective threats, the Soviets and Japanese did not fight each another until the 9 August Soviet–Japanese War, three months after the surrender of Germany. Japan thus fought a two-front war as well and split its forces between China in the Second Sino-Japanese War and the United States in the Pacific Theatre. The Soviet Union later invaded Manchuria, worsening the situation for Japan.
In the case of the United States, the Pacific Theatre was primarily a naval and air effort despite losing ships during the 1941 Pearl Harbor Attack while ground forces were used in Europe. Likewise for Japan, most ground troops were fighting China, and the Pacific Theatre was also primarily a naval and aerial battle. It was also the first time the United States ever fought a two-front war.
A major rationale for the American 600-ship Navy plan in the 1980s was to threaten the Soviet Union with a two-front war, in Europe and the Pacific Ocean, in the event of hostilities.
- Cathal J. Nolan (2002). The Greenwood Encyclopedia of International Relations: S-Z. Greenwood Publishing Group. pp. 1712–. ISBN 978-0-313-32383-6.
- Uri Friedman (March 3, 2017). "America's Two-Front War of Ideas". The Atlantic Monthly Group. Retrieved May 19, 2019.
- Lawrence Allen Eldridge (18 January 2012). Chronicles of a Two-Front War: Civil Rights and Vietnam in the African American Press. University of Missouri Press. ISBN 978-0-8262-7259-1.
- Michael Peck (November 11, 2018). "Germany Could Have Won World War I. Here's How". Center for the National Interest. Retrieved May 19, 2019.
- Jeffrey Billman. "The Effects of the Two-Front War on Germany During WWII". Leaf Group Ltd. Retrieved May 19, 2019.
- Higgins Trumbull (April 1, 1967). "Hitler And Russia: The Third Reich in a Two-Front War, 1937–1943". Oxford University Press. Retrieved May 19, 2019.