The Insular Force of Guam

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They were classed as native seamen
From http://www.matrixgames.com/forums/tm.asp?m=2880314
There were less than 200 members (at full strenght, which they never were) armed with Springfields and two Lewis guns (one of which was always broken). They had no artillery,mprtars or even hand grenades. In essense, they were an auxilary unit of the "police force". The "police force"? That was less than 100 US Marines, who were armed in a similar nature. On invasion day , the insular force put up a spirited fight for the Govenors house. They lost two members , and surrendered half an hour later (pretty much out of ammo). The USMC forces had even less, and didn't last much longer.

But what about these guys are they ISF as well?

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Khaki drill uniforms with white embellishments

The bottom picture is probably members of the Guam Insular Patrol Force which later became the Guam Police Department in 1949. The Guam Insular Guard was the predecessor of the modern Guam Army National Guard but was run by the US Navy hence the uniforms.

Guam remains a US territory and is expected to hold a referendum on becoming an state of the United States as opposed to remaining a territory in 2012.