Throughout the 1580s, Mirza Ali Beg reportedly led several expeditions in the attempt of the Ottoman Empire to contest the Portuguese control of the Persian Gulf, Red Sea, and Indian Ocean down the Eastern Coast of Africa.
[1] Ali Beg would return from his first expedition to the Swahili Coast in 1586 resoundingly successful, having "managed to secure the allegiance of every major Swahili port town except Malindi, to capture three fully laden Portuguese vessels, and to return safely to Mocha with some 150,000 cruzados of booty and nearly sixty Portuguese prisoners.
This would ultimately cost Ali Beg and the Ottomans, with his fleet being defeated in 1589 in Mombasa not only by the Portuguese but also a surprise third faction of supposed Zimba cannibals that ambushed them during battle.
Ruy Lopes Salgado, the captain responsible for defending the Swahili coast, chose to hide in Malindi rather than attempt to stop the privateer.
[4][page needed] In the Spring of 1589, Mir Ali Beg arrived in Mombasa to prepare for the oncoming Portuguese attack.
Although Ali Beg only had five galleots and approximately 300 men under his control to combat the strong Portuguese fleet, he was also given a large amount of artillery to use on land.
Mir Ali Beg would seek refuge inland for a couple of days while the Portuguese remained hesitant to leave the harbor, but that would change when the Zimba chief talked to the Portuguese commander and declared an alliance, prompting De Souza Coutinho to immediately head to capture Ali Beg and his men.
[2] Ali Beg appeared relieved to be captured by the Portuguese as opposed to the Zimba, saying, "I do not lament my adverse fortune, for such is the nature of war, and I would much rather be a captive of the Christians, as I was once before in Spain, than food for the barbarous and inhuman Zimba.”[6] After his defeat and subsequent capture in March 1589, Mir Ali Beg was taken to Lisbon where he would convert to Christianity and change his name to Francisco Julião, and live out his days as a prisoner.
It has been suggested they could have been anything from a migrating Maravi warriors to a mercenary army hired by discontented Mombasans or perhaps a local group that preferred Portuguese influence to that of Ottoman interlopers.