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.