“I wasn’t talking about the American invasion in 1944, but the Japanese militarization of the island in 1941. The League of Nations Class C mandate was not supposed to include militarization, thus it was technically an invasion.”
Japan pulled out of the League in 1933. It is widely regarded that the militarization of Saipan began then.
Even then, the state department blocked requests by the defense department to beef up the defense capability of Guam, believe it or not. They said it would be provocative. Yeah, sort of like buying a home defense shotgun would provoke a home invader.
It is amazing that Guam held out as long as they did given that their defense was hamstrung so much by our own government.