Damascus fell in September 634 and Emesa fell in March 635. In the year 635, Emperor Heraclius successfully allied with Sassanid Persian Emperor Yazdegerd III on Yazdegerd III's request to crush the Muslim power. A well coordinated plan was agreed to launch a massive counterattack against Muslims in Iraq and Syria at once so that Muslims, because of the resulted pressure may retreat back to Arabia where they may be dealt in detail later, either by invading it or by economical and trade blockage. Caliph Umar successfully tackled the alliance by putting pressure tactics on Byzantine front and deceptive tactics on Persian front and engaging Yazdegerd III into negotiations, this rendered the alliance and a would-be decisive plan abortive. The Byzantine forces were decisively defeated in Battle of Yarmouk fought in August 636, Persian army was defeated in Battle of Qadisiyyah three months later in November 636. Muslim victory pertinently ended Byzantine rule south of Anatolia, and Jerusalem fell in April 637 after a prolonged siege, Umar personally came to receive the key to the city by the Greek Orthodox patriarch, Sophronius, and was invited to offer prayers at the Church of the Holy Sepulchre. Umar chose to pray some distance from the Church, so as not to endanger its status as a Christian temple. Fifty-five years later, the Mosque of Omar was constructed on the site where he prayed. After the fall of Jerusalem, Umar permitted Jews to practice their religion freely and live in Jerusalem. ("See: Covenant of Umar I")