Bases and Installations are not the same thing.
The number of US troops in Germany peaked during the Cold War at around 400,000 in 1962. This was due to the tensions between the US and the Soviet Union, with the border between East and West Germany at the forefront.
The US Congress has the power to appropriate funding for military operations through its power to raise and support armies, and to make laws that are necessary and proper for carrying out its war powers. However, Congress's power to appropriate funding for the military is limited to two years.