Japan gives notice of withdrawal from the League of Nations, effective two years later, but keeps the mandate.

What happened

The mandate terms barred fortifications and military bases, but after announcing its withdrawal from the League, Japan made clear it would keep the islands. Japanese sources say base building then sped up, especially in Chuuk Lagoon.

Why it matters

Chuuk Lagoon became a major Japanese naval base, which US forces struck in February 1944.