1545: 4000+[note 1] 1546–47: 19,000[2] 1545: 6 regiments[3] 1546–47: 20,000+ [4] The Toungoo–Mrauk-U War (Burmese: တောင်ငူ–မြောက်ဦး စစ်) was a military conflict that took place in Arakan (present-day Rakhine State of Myanmar) from 1545 to 1547 between the Toungoo Dynasty and the Kingdom of Mrauk U.

Although Min Bin left the alliance in the same year, King Tabinshwehti of Toungoo was determined to repay the favor.

[5] On 30 January 1547, the two sides agreed to a peace treaty that allowed an orderly withdrawal of Toungoo forces from Arakan.

[7] On the western coast, the Kingdom of Mrauk U was ascendant at the expense of a weak Bengal, extending its reach into the Ganges Delta in 1533.

After his army's crushing defeat at Padaung Pass, King Min Bin of Mrauk U left the alliance.

Convinced that Toungoo's guns would eventually point toward his kingdom, Min Bin beefed up the already formidable defenses around his capital.

[11] In the following three years, Toungoo completed its takeover of central Burma up to Bagan, which Ava formally ceded in exchange for peace in 1545.

His high command had been joined by former Hanthawaddy generals like Saw Lagun Ein and Smim Payu, and Portuguese mercenaries like Diogo Soares.

[20] Nonetheless, Tabinshwehti was not yet ready to start another full-scale war, given the developing situation in Upper Burma where Ava was facing a serious rebellion backed by Mohnyin.

[1][17] By mid-1546, the war in Upper Burma had reached a stalemate with the rump Ava Kingdom further splitting into two halves: the Mohnyin-controlled west of the Irrawaddy (present-day Sagaing Region and southern Kachin State), and Onbaung–Hsipaw-controlled eastern half (approximately, northern Mandalay Region and western Shan State).

[23] The Toungoo command cautiously decided that it was safe to launch a major campaign in Arakan in the following dry season.

[2] Meanwhile, a number of rearguard forces were deployed across the kingdom: the capital Hanthawaddy was defended by regiments commanded by Baya Gamani and Binnya Ein; the southern province of Martaban (present-day Mon State) by Saw Binnya U of Mawlamyine; Toungoo in east-central Burma by Mingyi Swe; Pyay in west-central Burma by Thado Dhamma Yaza I of Prome; and key towns along the northern border, Bagan, Salay, and Taungdwingyi by their local governors.

[25] These were the result of the multi-year defensive construction works project Min Bin launched right after his conquest of Bengal in 1533.

The defense works were initially begun to protect the capital region from rampant seaborne raids by Portuguese pirates, and later expanded to defend against Toungoo invasions.

A 35-ship Arakanese fleet, largely manned by Portuguese mercenaries and commanded by Min Dikkha, sailed down to Cape Negrais to block a possible seaborne invasion.

[note 10] The Mrauk U navy, waiting around Cape Negrais, initially thought about engaging Toungoo vanguard squadrons but decided against it when they saw the size of the invasion fleet.

[2] Tabinshwehti appointed Min Aung Hla as the viceroy of Thandwe, and left Nanda Kyawhtin, Governor of Thanlyin, in charge of the city's defenses.

But Min Bin opened the sluices of the city's reservoirs, flooding out many Toungoo troops and creating an impassable moat.

Further complicating matters, Tabinshwehti received news that Siamese forces had occupied Dawei, which Toungoo had claimed.

Given that the home country was still vulnerable to possible external attacks, they advised the king to accept a compromise with Min Bin.

[30] Likewise, Min Bin may have wanted a quick truce since he had heard that Tripuri marauders were raiding his northern possessions in Bengal down to Ramu.

[32] The Arakanese chronicles however say that Toungoo proposed first, stating that Min Bin at first refused to see Tabinshwehti's emissary Bayinnaung, and agreed to see him only on the second day.

[note 11] Toungoo forces withdrew from Mrauk U beginning on 2 February 1547, but two regiments remained stationed at Thandwe for three more months per agreement.

Bayinnaung readily took in Prince Upayaza of Thandwe, who had lost the throne to Min Dikkha, awarded him the style Thiri Dhammathawka in 1554, and married him to one of his nieces.