alternatehistory.com

Part 2 Countdown to War
While the Philippines shifted from a sleep colonial garrison to an armed force preparing to defend an eventual independent nation and US ally, the Pacific Fleet continued its peace time rituals throughout the 1930s. It is not until the Fall of France and the new aggressive diplomatic moves by Japan aimed at the Dutch East Indies and French Indochina that the US Navy shifts to becoming a deterrent force and preparing for a potential war. The US Military receives even greater resources and the US Navy begins a shooting at German U-Boats in the Atlantic and being shot at as well. President Roosevelt determines that Japan must be deterred from war so that the United States can concentrate on the Nazi threat, and the commanders in the Philippines and Hawaii both take active and indeed aggressive steps to prepare their forces for war in the hopes of deterrence.

That this deterrence failed is of course well known. But the steps commanders took in the Philippines and Hawaii, as well as decisions made in Washington, were to ensure that when war came, the United States and the Republic of the Philippines military forces would put up an effective fight. The Americans and Filipino's developed a very robust defense force in the Philippines, while in Hawaii the development of a unified air defense command and parallel scouting force would lay the important groundwork for joint operations by US Navy and Army forces in the Pacific and Europe for the entirety of World War II and in the years since.

It is the seizure of northern French Indochina in September 1940 and the Japanese signature of the Tripartite Pact with Germany and Italy that made it clear that the United States would have to move more quickly from peace to readiness for war in the Pacific.