ed ▁on ▁ 2 0 ▁April ▁ 1 4 5 5 ▁by ▁Card inal ▁Pro t ode acon ▁Pro s per o ▁Col onna . ▁ ▁Not ▁quite ▁two ▁years ▁after ▁the ▁Fall ▁of ▁Constantin ople , ▁Cal li xt us ▁was ▁chief ly ▁concerned ▁with ▁the ▁organization ▁of ▁Christian ▁Europe ▁against ▁an ▁invasion ▁by ▁the ▁Tur ks . ▁An ▁extensive ▁building ▁program ▁under ▁way ▁in ▁Rome ▁was ▁cancel led ▁and ▁the ▁money ▁fun ne led ▁toward ▁a ▁cr us ade . ▁Pap al ▁n unci os ▁were ▁dispatch ed ▁to ▁all ▁the ▁countries ▁of ▁Europe ▁to ▁b ese ech ▁the ▁princes ▁to ▁join ▁once ▁more ▁in ▁an ▁effort ▁to ▁check ▁the ▁danger ▁of ▁a ▁Turkish ▁invasion . ▁Mission aries ▁were ▁sent ▁to ▁England , ▁France , ▁Germany , ▁Hung ary , ▁Portugal , ▁and ▁Arag on ▁to ▁pre ach ▁the ▁Cr us ade , ▁and ▁to ▁eng age ▁the ▁pray ers ▁of ▁the ▁faithful ▁for ▁the ▁success ▁of ▁the ▁enter prise . ▁It ▁was ▁by ▁order ▁of ▁Cal li xt us ▁III ▁that ▁the ▁b ells ▁were ▁r ung ▁at ▁m idd ay ▁to ▁rem ind ▁the ▁faithful ▁that ▁they ▁should ▁pray ▁for ▁the ▁w elf are ▁of ▁the ▁cr us aders . ▁ ▁The ▁princes ▁of ▁Europe ▁were ▁slow ▁in ▁respond ing ▁to ▁the ▁call ▁of ▁the ▁po pe , ▁largely ▁due ▁to ▁national ▁rival ries . ▁England ▁and ▁France ' s ▁H undred ▁Years ' ▁War ▁had ▁just ▁ended ▁in ▁ 1 4 5 3 . ▁Forces ▁led ▁by ▁John