The Global Culture War is a conflict between the Polity and the Union. This war began in 2068 with the Union's unprecedented attack on New York City. The Vanguard has been on the defensive since their withdrawal from the city.
In the years before the war, the Polity and the Union were both in a state of cold war. It was implied that there were many border clashes, airspace intrusions and terrorist attacks during the last pre-war years, but no major open conflict had occurred during this period.
During President Bartlet-Young's address to the United Nations, the Union unleashed mass swarms of Nanotech into the building through an unknown method, and at the same time, Union troops, drones, Spider Tanks, Behemoths, and air force units were invading New York City. By the time the Vanguard has respond, the Union forces have already taken most of the city. When the Vanguard sees what happened, they order Interceptor and Razor pilots to provide support of the ground forces, primarily composed of Striders, Armor and Infantry, and try to retake the skies over New York City. However, they are unable to repel the invaders, and are forced to retreat, leaving New York in Union hands and signaling the start of the war.