▁the ▁Christian ▁kingdom s ▁did ▁not ▁press ▁their ▁advantage ▁and ▁gave ▁the ▁Mo ors ▁time ▁to ▁re build ▁their ▁forces . ▁ ▁Fall ▁of ▁Al ge cir as ▁In ▁August ▁ 1 3 4 2 , ▁Alfonso ▁XI ▁laid ▁sie ge ▁to ▁the ▁strateg ic ▁port ▁of ▁Al ge cir as ▁on ▁the ▁western ▁side ▁of ▁the ▁Bay ▁of ▁Gib ral tar ▁with ▁a ▁Cast ilian ▁naval ▁force ▁block ading ▁the ▁city ' s ▁access ▁to ▁the ▁sea . ▁The ▁twenty - month ▁sie ge ▁was ▁notable ▁for ▁its ▁use ▁of ▁can non ▁by ▁the ▁Mo ors ; ▁it ▁was ▁one ▁of ▁the ▁first ▁occasions ▁that ▁guns ▁were ▁used ▁effectively ▁in ▁European ▁war fare . ▁Although ▁they ▁succeeded ▁in ▁holding ▁off ▁the ▁Cast ili ans , ▁neither ▁side ▁was ▁able ▁to ▁gain ▁the ▁upper ▁hand ▁until ▁the ▁Cast ilian ▁fleet ▁managed ▁to ▁lay ▁a ▁bo om ▁across ▁the ▁entrance ▁to ▁the ▁har bour ▁of ▁Al ge cir as , ▁comple ting ▁the ▁block ade . ▁With ▁the ▁g arrison ▁now ▁completely ▁cut ▁off , ▁Y us uf ▁I ▁accepted ▁defeat ▁in ▁March ▁ 1 3 4 4 ▁and ▁proposed ▁a ▁fifteen - year ▁tr uce ▁in ▁exchange ▁for ▁the ▁surrender ▁of ▁Al ge cir as , ▁perm itting ▁the ▁g arrison ▁to ▁withdraw ▁peace fully , ▁and ▁the ▁res umption ▁of ▁t ribute ▁pay ments ▁by ▁Gran ada ▁to ▁Cast ile . ▁Alfonso ▁XI ▁accepted ▁the ▁proposal ▁but ▁reduced ▁the ▁tr uce ▁period ▁to ▁ten ▁years . ▁ ▁The ▁tr uce ▁only ▁last