
Comments:
- Truk and Ulithi are still very good and have enormous anchorages inside their coral reefs. Truk has the benefit of a big anchorage and a large island for airfields.
-Yap appears to have three small potential anchorages within her reef based on looking at some maps on the web.
- Zamboanga is the closest map feature to Dumangilis Bay which was selected by the USN as their advanced base in the Philippines in the late 1920s after the threat of Japanese airpower made Manila an untenable fleet base in US estimation. The anchorage was judged sufficient for 400+ ships as well as sea planes with plenty of solid ground around the bay to support airfield construction and port facilities.
- Lahaina Roads was selected as the concentration point for the US expedition to the Philippines after the armada grew to 700 to 800 ships and outgrew the space at Pearl Harbor. The figure in the table is the water area of Maui County, and includes the stretch between Maui/Lanai and Molokai. That's too deep and choppy for an anchorage, but the area from Kapalua down to Makena would be suitable with Maui sheltering the waters from the prevailing trades and the surrounding islands of Molokai, Lanai, and Kohoolave break up the ocean swell. The area there is certainly over 300 square miles with a typical depth of 100 to 300 feet.
- Back in the 1920s none of the mid-ocean locations (except for Guam and the Hawaiian islands) had over 20,000 people on them. Most were far less populated, hundreds to a few thousand.
What this does is suck the US counter-offensive after Wake and Guam fall into the Marshalls and the Carolines because that's where the good bases can be built. But that's what the historical naval planners realized. Unless the plan involved a virtually non-stop voyage from Pearl to the Philippines, these were the islands that needed to be captured to serve as advance bases. There was evolution in the plan over time insofar as the early version of WPO that called for an advance through the Mandates (1922) involved a mopping up operation that captured all the islands while the historical implementation in WW2 featured island-hopping and bypassing non-critical garrisons.