Pope Calixtus III reiterated the main points of "Dum Diversas" in his bull four years later, "Inter Caetera". Once again the Pope was attempting to raise support for a campaign against the advance of the Turks. Nuncios had been dispatched to all the countries of Europe to beseech the princes to join once more in an effort to check the danger of a Turkish invasion. However, the princes of Europe were slow in responding to the call of the pope, largely due to their own national rivalries. On 29 June 1456, Callixtus ordered the church bells to be rung at noon (see noon bell) as a call to prayer for the welfare of those defending Belgrade. Forces led by Janos Hunyady, Captain-General of Hungary, met the Turks and defeated them at Belgrade on 22 July 1456.