Visited the East Coast Memorial today- makes me question; What were the specifics involved that allowed the Allies to defend from 1939 - 1945 during WWII? I’m not to well versed in naval warfare, but this seems like an extraordinary length of time to defend the area.

by whereisdani_r

thefourthmaninaboat

Could I just ask precisely which area you're asking about? The Eastern Seaboard of the US/Canada?

Bacarruda

This answer on the Battle of the Atlantic may be helpful to you!