


The United Kingdom's military intelligence organization, MI9, decided that, as an alternative to exfiltrations of downed airmen, to gather airmen into isolated forest camps where they could await the arrival of allied armies. However, in 1944, heavy allied bombing of railroads and other transportation infrastructure made escape to neutral counties increasingly difficult in the run-up to the Normandy Invasion of France.

Escape and evasion lines operated by civilian volunteers in France, Belgium, Netherlands, and Denmark helped about 5,000 downed allied airmen evade capture by the Germans and escape to a neutral country such as Spain. Tens of thousands of allied aircraft were shot down or crash landed in Nazi-occupied Europe during World War II. Jean de Blommaert, head of Marathon in France.
