 Complete the following phrase:  The expansion of Muscovite Russia under Ivan IV 15331584 into the Volga and Caspian region at the expense of the Tatar khanates disrupted the northern pilgrimage and trade routes. A highly ambitious plan to counter this conceived by Sokollu Mehmed Pasha, Grand Vizier under Selim II, in the shape of a Don-Volga canal begun June 1569, combined with an attack on Astrakhan, failed, the canal being abandoned with the onset of winter. Henceforth the Empire returned to its existing strategy of utilizing the Crimean Khanate as its bulwark against Russia. In 1571, the Crimean khan Devlet I Giray, supported by the Ottomans, burned Moscow. The next year, the invasion was repeated but repelled at the 