From the very beginning, the Spaniards recruited Chamorro men for military and paramilitary service. Even in the fighting between the Spaniards/South Americans/Filipinos and the Chamorros, some Chamorros fought on the Spanish side.
Over the years, local men were formed into militia units. Names and structures changed every so often, but basically the local militia did guard duty and police work. The men usually had to pay for their own uniforms and supplies.
Chamorro Militia Members in 1837
The Chamorro militia was headed by a Sergeant Major, but that position was vacant in 1837. The next in rank was the 1st Adjutant, who was none other than Silvestre Inocencio Palomo, the father of the future priest Pale' Jose Palomo. The 2nd Adjutant was Cecilio Camacho, one of the patriarchs of the Camacho clan that gave us two governors (Carlos and son Felix) and other island politicians, professionals and businessmen.
Other high-ranking militia members were : Jose Joaquin Cruz, Jose Martinez, Jose Flores, Bernardino Lizama, Felipe Lizama, Jose Aguilar, Francisco Salas, Juan Salas, Jose Aguon, Ramon Borja, Alejandro de Leon Guerrero, Rosauro Cruz, Jose de Torres, Vicente Martinez, Joaquin de Torres. The drummer was Zacarias Quitugua.
As can be seen, the overwhelming majority of these men were Hagåtña mestizos; people of mixed Chamorro and outside blood. Only Jose Aguon, and the drummer Zacarias Quitugua, had Chamorro surnames and they were probably mestizos as well. Even among the ordinary soldiers in 1837, only two had Chamorro last names : Jose Taisague and Tomas Muña.
These Hagåtña militia men were fanned out to the outlying villages as well as Fort Santa Cruz in Apra Harbor for short terms; then they would return to Hagåtña . But some did stay in the outlying villages and that's how these Hagåtña names took root outside the capital city.
(Note : The pic above is not of Guam, but of the Philippines. It is just to give an idea what the Chamorro militia may have looked like in a general way. I have yet to come across a photo of Chamorro militia men during Spanish times.)