Apparently when the Americans first officially went to the Moon they found it well occupied with various groups holding their own terrain with strict agreements in place to prevent wars.
There was no room for the Americans. Still, it seems that the Nazis (with alien support) made their first landing in 1944 - and the Americans when they arrived are said to have spent their first night in the German base. After all it was German scientists that provided the technology for the Americans.
Who were the Paperclip Germans really working for?