▁the ▁Third ▁Military ▁District ▁( the ▁miss ions ▁at ▁San ▁Luis ▁Ob is po , ▁San ▁Miguel , ▁San ▁Antonio , ▁So led ad , ▁San ▁Carlos , ▁and ▁San ▁Juan ▁B aut ista , ▁along ▁with ▁Villa ▁Bran c if orte ▁[ S anta ▁Cruz ]); ▁and ▁ ▁El ▁Pres id io ▁Real ▁de ▁San ▁Francisco ▁founded ▁on ▁December ▁ 1 7 , ▁ 1 7 7 6 ▁– ▁responsible ▁for ▁the ▁defense ▁of ▁all ▁install ations ▁located ▁within ▁the ▁Four th ▁Military ▁District ▁( the ▁miss ions ▁at ▁Santa ▁Cruz , ▁San ▁José , ▁Santa ▁Clara , ▁San ▁Francisco , ▁San ▁Rafael , ▁and ▁Sol ano , ▁along ▁with ▁El ▁P ue blo ▁de ▁San ▁José ▁de ▁Gu ad alu pe ▁[ San ▁Jose ]). ▁ ▁El ▁Pres id io ▁de ▁Son oma , ▁or ▁" S on oma ▁Bar ra cks " ▁( a ▁collection ▁of ▁guard h ouses , ▁stor ero oms , ▁living ▁qu arters , ▁and ▁an ▁observation ▁tower ) ▁was ▁established ▁in ▁ 1 8 3 6 ▁by ▁Mar iano ▁Gu ad alu pe ▁Valle jo ▁( the ▁" Command ante - General ▁of ▁the ▁Northern ▁Front ier ▁of ▁Al ta ▁California ") ▁as ▁a ▁part ▁of ▁Mexico ' s ▁strategy ▁to ▁halt ▁Russian ▁inc urs ions ▁into ▁the ▁region . ▁The ▁Son oma ▁Pres id io ▁became ▁the ▁new ▁headquarters ▁of ▁the ▁Mexican ▁Army ▁in ▁California , ▁while ▁the ▁remaining ▁pres id ios ▁were ▁essentially ▁abandoned ▁and , ▁in ▁time , ▁fell ▁into ▁ru ins