At Aden, Pasha Suleiman captured the city after inviting its ruler, Sheikh Amir bin Dawaud, favourable towards the Portuguese, aboard his ships, then hanging him.

[4][11] The expedition left Aden on 19 August and then called at Socotra, thereafter making its way to the western coast of Gujarat, despite losing some ships that got separated from the fleet during the passage of the Indian Ocean.

Under the command of Khadjar Safar – Coge Sofar in Portuguese, an Albanian renegade from Otranto and an influential lord in Gujarat[14] – the Gujarati forces began crossing the channel of Diu onto the western side of the island on 26 June 1538, being held back by the city's western walls just long enough for the Portuguese to fill their water reserves and burn their supply storages in the city before finally retreating to the fortress on the eastern end of the island.

Lopo de Sousa Coutinho, who would later write his memoirs on the siege, distinguished himself on 14 August after leading 14 Portuguese in a sortie into the city to capture supplies, defeating 400 soldiers of Khadjar Safar.

On 7 September a strong storm fell upon Diu, damaging part of the Ottoman fleet (and helping the Portuguese restore their water supplies), after which the Turks began unloading their artillery and a further 1,000 men, and raising a number of defensive and siege works around the fort.

Not knowing what to make of it, we shortened sail and hove to for the rest of the night until daybreak, when we got a clear view of the fortress surrounded by an enormous number of lateen-rigged vessels.

They were huge galleys, with their fore-and-aft sails in a checkerboard pattern of green and purple, the deck awnings literally covered in flags, and long banners streaming so far down from the mastheads that the ends brushed the surface of the water.

It read: I have surrendered to the great captain Çoleymam baxá through an agreement sealed in gold under his name, in which he granted us our lives, liberties, belongings and slaves, old and young, except the weapons and artillery: and had us go greet him on his galley, and as we were led to the city, they divided us by the houses, in groups of two: me and Gonçalo D'Almeida my cousin, and António Faleyro were taken to Suleiman's bastard galley, who received us well and gave each of us fine clothes; after which I told him to spare me such procedure of his and release us (as had been promised) and he responded that we ought not to wear ourselves out, for he had fulfilled his part.

[21]The writer Gaspar Correia provided a different account of the exchange, however it is not in accordance with that of the veteran Lopo de Sousa Coutinho, who personally participated in the siege.

After seven days of bombardment, part of the bulwark of Gaspar de Sousa collapsed and the Turks attempted to scale it "with two banners", but were repelled with heavy losses to bombs and arquebus fire.

Ever cautious, António da Silveira ordered the sentries to be alert – at daybreak, 14,000 men divided in three "banners" attempted to scale the fortress as it was bombarded with no regard to friendly fire.

With his relation with Coja Safar and the Gujaratis degrading and increasingly fearful of being caught off-hand by the Viceroy's armada, on 1 November the Pasha finally decided to abandon the siege and began re-embarking his troops.

In reality, it was just a forward fleet under the command of António da Silva Meneses and Dom Luís de Ataíde, dispatched from Goa with reinforcements, supplies, and news that the governor would depart soon to their aid.

The governor had assembled a relief force of 14 galleons 8 galleys, several caravels and over 30 smaller oar ships, but on 14 September the new viceroy appointed by Lisbon arrived, and demanded the immediate succession in office.

[27] By the end of 1537, reports on Ottoman preparations in Egypt had reached Lisbon through Venice, and King John III promptly ordered a reinforcement of 11 naus and 3,000 soldiers, of which 800 were fidalgos, to be dispatched to India as soon as possible along with the new viceroy, Dom Garcia de Noronha.

At Goa however, Dom Garcia considered the relief force organized by governor Nuno da Cunha to be insufficient, though the Portuguese veterans in India argued otherwise.

The viceroy remained in Goa for two more months, organizing his forces until he had gathered an imposing fleet, which according to João de Barros numbered 170 sail and 4500 Portuguese soldiers, and according to a detailed report by Francisco de Andrade, was composed of 152 vessels, which included 9 heavy carracks, 14 galleons, 13 small carracks, 8 war-caravels, 5 latin caravels, 1 bastard galley, 13 royal galleys, 15 galleots, 11 Mediterranean brigantines, 2 albetoças, 18 light galleys and 44 light vessels and oarcraft, bearing 5000 Portuguese soldiers, 3000 Indian auxiliaries, 1500 Portuguese sailors, uncounted number of native sailors, oarsmen and combat slaves and a little under 400 heavy cannon and 600 light cannon.

[30] The defeat of the combined Turkish and Gujarati forces at Diu represented a critical setback in Ottoman plans for expanding their influence into the Indian Ocean.

Without a suitable base or allies, failure at Diu meant the Ottomans were unable to proceed with their campaign in India, leaving the Portuguese uncontested in the western Indian coast.

[4] The veteran Lopo de Sousa Coutinho later recounted that "it was said" that the Portuguese who had surrendered to Suleiman Pasha were all killed off in the Red Sea, on their way back to Egypt.

[4] Turkish and Indian historians pass over the 1538 siege in very summary ways and attributed its outcome to the failure of the Gujaratis to provide the Turks with adequate supplies.