Major hostilities between Portugal and the Ottoman Empire had begun in 1538 when the Turks, with fifty-four ships, laid siege to Diu, which had been built by the Portuguese in 1535.

The Ottoman fleet had been led by Suleiman I's emissary Hussein Paşa, however the attack had not been not successful and the siege was lifted.

The Portuguese under Estêvão da Gama, having left Goa on December 31, 1540 and reaching Aden on January 27, 1541, attacks the Ottoman fleet near Suez Harbor.

The fleet had reached Massawa (February 12), where Gama had left a number of ships and continued north.

Reaching Suez, he discovers that the Ottoman naval base has long known of his impending raid, and foils his attempt to burn the beached ships.

Gama is forced to retrace his steps to Massawa, although he pauses to attack the port of El-Tor on the Sinai Peninsula.

Estêvão da Gama (eldest son of the famous navigator Vasco da Gama and now Portugal’s Viceroy of India), returns to Massawa on May 22, 1541, to rejoin the ships he has left here.

While at Massawa, he attempts to salvage something from this raid by dispatching an expeditionary force under his younger brother Cristavão to assist the beleaguered Emperor of Ethiopia, who is now Gelawdewos; the Portuguese are mindful of their need for a mainland ally in East Africa.

Four hundred Portuguese men-at-arms are selected, seventy of whom are also skilled artisans or engineers, and one hundred and thirty slaves for this expedition, equipped with about a thousand arquebuses, an equal number of pikes and several bombards.

After being landed at Massawa and Arqiqo, the next port south of Massawa, the men began their trek inland to Debarwa, the capital of the Bahr negus, or Ethiopian viceroy for the northern provinces.

The Portuguese reach Debarwa after a march of eleven days on July 20, to learn that the rainy season renders further travel impossible.

Cristavão will not allow his men to pass the months in idleness, and has them construct sleds for the bombards and mount raids on nearby villages that have accepted Ahmed Gragn's rule.

He also learns from the Bahr negus that Queen Sabla Wengel is camped nearby on top of a mountain that Ahmed has been unable to reduce by siege.

With one hundred men, he marches to the mountain, and invites the queen to join him; she does so, bringing her entourage of thirty men and fifty women, all of who are received with careful ceremony.

The Portuguese continue south once the rains end.

Gama, after months of being slowed by their equipment, decides to leave half of it in an arsenal on Debre Damo.

His army passes the Church of St. Romanos around Christmas of 1541.

Taddesse Tamrat, an Ethiopian historian writes, "The Muslim occupation of the Christian highlands under Ahmad Gragn lasted for little more than ten years, between 1531 and 1543. But the amount of destruction brought about in these years can only be estimated in terms of centuries."

Gama, after celebrating Epiphany in the province of Agame in January 1542, has his first encounter with the Muslim troops on February 2 at the Battle of Bacente, which Whiteway identifies with Amba Sonaut in Haramat.

The invaders had taken possession of a hill from which they made raids into the countryside.

Although Queen Sabla Wengel advises Gama to march around this hill, advising him to wait until her son Emperor Gelawdewos could arrive from Shewa and join him, he believes that failing to engage the invaders will make the natives distrust his troops, and that they would then stop bringing food and supplies.

Fortunately, the engagement is an unquestioned success, and Gama's men take the hill despite superior enemy numbers, losing only eight men.

Two Portuguese arrive at the end of February from a ship anchored at Massawa, escorted by six people native to the area.

Gama responds with a detachment of forty men to make contact, obtain supplies, and exchange news.

This group fails to reach the ship before it sails, and the only outcome is that these soldiers and their captain are absent for the next battle, which is against Ahmad Gragn himself.

The events at Bacente have alerted Ahmad Gragn, as Queen Sable Wengel had feared, that a hostile army has entered the area, and he marches north to confront it, meeting Gama at Jarte (which Whiteway identifies with the province of Wagarta).

The Imam makes the first contact, sending a messenger to Gama to demand that the Portuguese force either leave Ethiopia, join Ahmad Gragn, or be destroyed.

On the Imam's orders, the messenger produces the gift of a monk's habit, an expensive insult to Gama.

Gama responds with his own messenger, who delivers "a few lines in Arabic", stating that he had come to Ethiopia "by order of the great Lion of the Sea" and on the "following day he [Ahmad Gragn] would see what the Portuguese were worth", and delivers Gama's own insulting gift: a pair of "small tweezers for the eyebrows, and a very large mirror -- making him out [to be] a woman."

Two battles follow these exchanges at Jarta, the first on April 4 and the next on April 16.

The first battle is a victory for the Portuguese, although Gama loses one of his captains: Ahmad Gragn is wounded, which forces his troops to retire to the far side of the plain.

The Portuguese, finding their encampment on the battlefield becoming unbearable, move across the plain next to the enemy camp, which leads to the second battle.

This time, the Muslim army is even more soundly defeated, and according to Castanhoso, "The victory would have been complete this day had we only [had] a hundred horses to finish it."

Ahmad Gragn is forced to retreat further south, to a village Whiteway identifies as Wajarat.

With fortune against him, the local population now openly defies him by refusing to provide him supplies or soldiers.

Gama marches as far as Lake Ashangi, where, on the advice of Queen Sable Wengel, he makes camp on a hill in Wofla as the rainy season starts.

A Jew (possibly one of the Beta Israel) approaches Gama at some point late in the rains and tells him of a mountain stronghold that Ahmad Gragn's followers control weakly (identified by Whiteway as Amba Sel.

Gama is also at this time accurately informed about the Emperor Gelawdewos's true strength: the Ethiopian monarch is living as an outlaw in the south, with only sixty to seventy men in his army.

However, the mountain is the major barrier between the two allies, and Gama learns that the garrison has a large number of horses—a resource he had badly needed in his last battle.

Gama swiftly marches south with about a hundred men, and seizes control of the mountain.

Leaving thirty men behind to bring the horses, Gama leads his victorious men back to Wofla, to find Ahmad Gragn in position to attack that next morning.

Having successfully petitioned the governor of Zabid in South Arabia, as well as offering "much money" and submission to the official, Gragn receives a number of musketeers, many more than da Gama had.

Despite their bravery, the Portuguese are heavily defeated on August 28 at the Battle of Wofla, with only one hundred and seventy surviving the assault (counting the thirty men escorting the horses from the Hill of the Jews).

Gama, his arm broken from a bullet, is captured that night with fourteen companions by a Muslim patrol.

Cristóvão da Gama is brought to Ahmad Gragn's camp, where the Imam produces the tweezers Gama had given him and begins to pluck out his beard.

He is tortured in an attempt to force him to convert to Islam.

Castanhoso's—and Jerónimo Lobo's account after him—describe Gama's fortitude and death in language worthy of a hagiography, complete with miracles.

In the end, Ahmad Gragn chops off Gama's head and tosses it into a nearby spring, whose waters Castanhoso reports gained a reputation for giving "health to the sick.”

Ahmad Gragn, certain that the surviving Portuguese are scattered, without their firearms, and alone in a foreign land, concludes that this threat is ended, dismisses all but two hundred of the foreign musketeers, and proceeds to his camp at Derasge on the shores of Lake Tana.

However, over one hundred and twenty men have joined Queen Sabla Wengel, who has taken refuge at the Mountain of the Jews.

Ten days later, her son, Emperor Gelawdewos, arrives and they take measure of their situation.

Using the arms stockpiled at Debre Damo, the Portuguese are able to rearm themselves; with the promise of their ability, Gelawdewos is able to raise a new army, which meets Ahmad Gragn at Wayna Daga on February 21, 1543.

The Portuguese musketeers aim their fire only at the Muslim musketeers, who had played a decisive part at Wofla—and at Imam Ahmad himself.

While the sources differ on the exact details, all agree that Cristóvão da Gama’s men killed Ahmad Gragn to avenge their commander's death.

Gelawdewos had devoted time and energy to rallying his people against Ahmad, a determination his chronicler credits with preventing Ahmad's forcible conversions from being permanent.

With Ahmad's death, Gelawdewos is not only able to eject the leaderless Muslim forces from the Amhara plateau, but also from the lowlands to the east, which include Dawaro and Bale.

The Ottomans, who had in 1541 contributed a force of nine hundred musketeers but have their own troubles to deal with in the Mediterranean, are unable to help Ahmad's successors.