The two principal belligerent powers were Germany and the Soviet Union, along with their respective allies. Though never sending in ground troops to the Eastern Front, the United States and the United Kingdom both provided substantial material aid to the Soviet Union in the form of the Lend-Lease program along with naval and air support. The joint German–Finnish operations across the northernmost Finnish–Soviet border and in the Murmansk region are considered part of the Eastern Front. In addition, the Soviet–Finnish Continuation War is generally also considered the northern flank of the Eastern Front.