In military terms, a two-front war is one in which fighting occurs in separate locations at the same general time. Some well-known two-front wars include both World Wars of the 20th century, the Napoleonic wars and several Israeli-Arab wars.
Two-front wars are taxing on a country's military because both troops and financial support must be spread among the locations. In World War II, for instance, the United States fought in the European theater against Hitler and his forces and in the Pacific against the Japanese threat. Separate troops and separate battle plans were necessary. The term "two-front war" is also used metaphorically to describe political attacks on an individual or party from different factions.