The military campaigns of the Aceh Sultanate challenge both the naval dominance of the Portuguese and the holdings of the Sultanate of Johor on Sumatra.

The victories of the 1520s expand Aceh’s territory, creating a powerful kingdom that will endure until the Aceh War (1873–1903). However, its struggle with the Portuguese remains relentless.

In 1527, Portuguese captain Francisco de Mello sinks an Acehnese vessel at the roadstead outside the capital, killing the crew. The following year, Simão de Sousa Galvão, forced by a storm to seek shelter in Aceh, is attacked by local forces—most of the foreigners are killed, and the survivors taken prisoner.

Sultan Ali Mughayat Syah begins peace negotiations, which halt a planned joint expedition by Aru and the Portuguese. However, new hostilities soon follow, and the sultan orders all Portuguese prisoners executed.

In 1529, Sultan Ali devises a surprise attack on Melaka, but news of the plan leaks, and the invasion never materializes.

The date of Sultan Ali Mughayat Syah’s death is uncertain, with later chronicles offering conflicting accounts—1511, 1522, or 1530. However, his gravestone records his passing as August 7, 1530, exactly one month before the death of his abdicated father, Syamsu. Both are buried in the palace compound of Kutaraja (now Banda Aceh).

Portuguese chronicler João de Barros alleges that Sultan Ali was poisoned by his wife, Sitt Hur, a sister of the ruler of Daya, in revenge for Aceh’s conquest of her homeland. She outlives him by twenty-four years, passing away on December 6, 1554.

Sultan Ali leaves behind two sons, Salahuddin and Alauddin al-Kahar. Salahuddin, who lacks his father’s military acumen, succeeds him on the throne, while his younger brother, Alauddin, will lay the true foundations of Aceh’s power after 1539.

Salahuddin's father sultan Ali had been engaged in a mortal combat against the Portuguese in Melaka, but hostilities had paused temporarily after his death.

However, in September 1537, an Acehnese fleet appears before Melaka, carrying a standing regiment of circa three thousand men.

The Acehnese land successfully but cannot invest the fortress.

After some ferocious fighting, they have to withdraw with great losses after two days.

Since the expedition is not mentioned in the local chronicles we cannot be sure that Salahuddin was still the ruler at this time.

From the account of Fernão Mendes Pinto it appears that his brother "Alaradim" (Alauddin) was already on the throne by 1539.

The much later chronicle Bustanus Salatin will alleges in about 1640 that Salahuddin lived for nine years after his deposition until his death in 1548.

It is thus somewhat unclear whether he was deposed before or after the launch of an unsuccessful attack on Melaka.

Hoesein Djajadiningrat believed that the coup came first and the attack was led by Alauddin al-Kahar, while Denys Lombard places the coup two years after the attack, which he believes was led by Salahuddin himself.

The Rise of Sultan Alauddin Ri'ayat Syah al-Kahar

Following the death of Sultan Ali Mughayat Syah in 1530, his eldest son, Salahuddin, assumes the throne. However, his rule proves ineffectual, leading to instability within the sultanate.

The queen mother, Sitt Hur, wields considerable influence over state affairs, appointing Raja Bungsu as regent. His authority is symbolized by a green payung (parasol), and his residence is strategically located opposite the royal palace.

Meanwhile, Sultan Ali’s younger son, Alauddin, governs Samudra Pasai, which Aceh had conquered in 1524. Dissatisfied with conditions in the capital, he orchestrates a royal coup in 1537 or 1539, overthrowing the regent and killing Raja Bungsu. He then imprisons Salahuddin and the queen mother, both of whom die years later—Salahuddin in 1548 and Sitt Hur in 1554.

Now in full control, Alauddin ascends the throne under the regnal title Sultan Alauddin Ri'ayat Syah al-Kahar. In Acehnese tradition, he is remembered as a brilliant organizer of the Acehnese state. He is often credited with structuring society into administrative lineage groups (kaum or sukeë), though historical sources differ on whether this attribution is accurate.

Alauddin’s Military Campaigns

Sultan Alauddin’s expansionist ambitions begin in 1539, when he wages war against the Batak people to the south of Aceh.

Portuguese traveler Fernão Mendes Pinto recounts that the sultan demanded the Batak king convert to Islam and, upon his refusal, launched a military campaign against him. Pinto’s account is detailed and vivid, but its reliability is questionable, as no comprehensive Batak kingdom is attested in other historical sources.

The Acehnese army at the time reportedly included Turkish contingents, as well as warriors from Cambay and Malabar, reflecting Aceh’s growing connections with the broader Islamic and Indian Ocean worlds.