The American 1st Army is one of the oldest field armies of the United States military. In R.U.S.E., it partook in the Invasion of Germany and the subsequent Soviet-Allied War. It is one of the four armies that can be chosen by Joseph Sheridan in the last two missions.
Following his actions at Bastogne, Sheridan is put in charge of this army. The 1st advances into Germany under Joe's command, scoring many victories along the way. When a British intelligence agent is captured at Colditz Castle, the Army attacks the region, quickly conquering it.
The American First Army then races to beat the Soviets to the Elbe, succeeding only by a few hours. After Germany surrenders, the Army begins garrison duty along side the Russians. Once Sheridan finds out about the V-2s, he can call on his army to fight the Soviets, or alternatively other allied forces. He may also call upon them in the final battle against the 8th Guards Army.
Being on the front line, the First Army employs the latest assortment of US tanks and aircraft, from Pershings to B-17 Flying Fortresses. Although the First Army apparently retains older models of aircraft, such as P-40 Warhawks, it comes with a mixed bag. Under Sheridan's command, the Army also tests prototype weapons, such as Calliope Rocket launchers. This unit was the only one to use a Nuclear Long Tom.