Complex sentence: However, at the time business interests came first and Hamilton was asked to continue in his position until the fall of France in 1940, after which Hamilton and his staff had to make an unorthodox exit out of Europe through Spain.
Split into simpler sentences: However, at the time business interests came first and Hamilton was asked to continue in his position until the fall of France in 1940. At which time, Hamilton and his staff had to make an unorthodox route out of Europe through Spain.