Classical Age of the Ottoman Empire
Expansion continued during the first half of the reign of Suleiman I (r. 1520-1566), who conquered first Belgrade (1521) and Rhodes, before invading Hungary in 1526, defeating and killing King Louis II in the Battle of Mohács and briefly occupying Buda. Lacking a king, Hungary descended into civil war over the succession, and the Ottomans gave support to John Zápolya as a vassal prince. When their rivals the Habsburgs began to achieve the upper hand, Suleiman directly intervened by again conquering Buda and annexing it to the empire in 1541. Elsewhere, Suleiman led major campaigns against Safavid Iran, conquering Baghdad in 1534 and annexing Iraq. Ottoman rule was further extended with the incorporation of much of North Africa, the conquest of coastal Yemen in 1538, and the subsequent annexation of the interior.
Safavid occupation of Basra (1697–1701)
Under Suleiman I's successor, Sultan Husayn (1694–1722), Iranian policy in relation to regaining Iraq did not change. According to Professor Rudi Matthee "this is hardly surprising", given that the Safavid army was weak at the time and the Shah himself was famous for his unassertive stance. Matthee does add that there is "great irony in it" given the "religious zeal" associated with Sultan Husayn. Unlike most of his predecessors, Sultan Husayn was a Safavid ruler who actively encouraged pilgrimages to the Shi'ite holy shrines in Iraq; Matthee thus adds that "during his reign Persian pilgrims visited the holy sites in unprecedented numbers". Sultan Husayn was also willing to spend resources of the Safavid state for the upkeep of the shrines in Iraq.