<P> The defeat convinced Manuel II to escape the city and travel to Western Europe for aid . During this time the reconciled John VII led the city's successful defence against the Ottomans . The siege was finally broken when Timur of the Chagatai Mongols led an army into Anatolia, dismantling the network of beyliks loyal to the Ottoman Sultan . At the Battle of Ankara, Timur's forces routed Bayezid I's forces, a shocking defeat for which no one was prepared . In the aftermath, the Ottoman Turks began fighting each other led by Bayezid's sons . </P> <P> The Byzantines wasted no time exploiting the situation and signed a peace treaty with their Christian neighbours and with one of Bayezid's sons . By signing the treaty, they were able to recover Thessalonika and much of the Peloponnese . The Ottoman civil war ended in 1413 when Mehmed I, with the support of the Byzantine Empire, defeated his opponents . </P> <P> The rare amity established between the two states would not last; the death of Mehmed I and the rise of Murad II in 1421 coupled with the ascent of John VIII to the Byzantine throne led to a deteriorated change in relations between the two . Neither leader was content with the status quo . John VIII made the first and foolish move by inciting a rebellion in the Ottoman Empire: a certain Mustafa had been released by the Byzantines and claimed that he was Bayezid's lost son . </P> <P> Despite the odds, a sizable force had mustered in Europe under his banner, defeating Murad II's subordinates . Murad II's furious reply eventually smashed this upstart and, in 1422, began the Siege of Thessalonica and Constantinople . John VIII then turned to his aging father, Manuel II, for advice . The result was that he incited yet another rebellion in the Ottoman ranks--this time supporting Murad II brother's claim, Kucuk Mustafa . The seemingly promising rebellion had its origins in Asia Minor with Bursa coming under siege . After a failed assault on Constantinople, Murad II was forced to turn back his army and defeat Kucuk . With these defeats, the Byzantines were forced once more into vassalage--300,000 coins of silver were to be delivered to the Sultan as tribute on an annual basis . </P>

The ottomans ended the byzantine empire by laying siege to which city