His early reign marked the continued ascent of the coastal kingdom, which reached full flight in 1599 by defeating its nemesis Toungoo Dynasty, and temporarily controlling the Bay of Bengal coastline from the Sundarbans to the Gulf of Martaban until 1603.

[note 2] In 1572, Phalaung succeeded King Sekkya, and made his eldest son Razagyi, only 15, heir-apparent with the style of Thado Dhamma Raza.

At the coronation ceremony, Razagyi was married off to Princess Nan Htet Phwa (နန်းထက်ဖွား, [náɴ tʰɛʔ pʰwá]), daughter of Sekkya and his first cousin, once removed.

His most prominent contribution during this period recorded in the Arakanese chronicles came in 1575 when he led a well armed naval and land forces in an expedition to Tripura.

The Arakanese forces, aided by Portuguese mercenaries and firearms, easily captured the Tripuri capital, after which Tripura agreed to pay tribute.

[6][7] In the later years, however, Phalaung began relying on his middle son Thado Minsaw, who became the commander-in-chief, for military expeditions, and appointed him king of Bengal.

For his part, he re-appointed Thado Minsaw as king of Bengal, essentially the viceroy of northern territories,[9] which included Chittagong, Noakhali and Tippera.

When Razagyi marched to Chittagong with a massive force after the rainy season, Thado Minsaw lost nerve and submitted without a fight.

[9] Razagyi was now the undisputed leader of a prosperous and militarily powerful kingdom that stretched from the Sundarbans in the northwest to Cape Negrais in the south.

King Nanda at Pegu (Bago) now controlled only parts of Lower Burma, and faced rebellions everywhere, including the city of Toungoo, the ancestral home of the Dynasty.

He ordered a massive mobilization drive across the entire kingdom, from the Ganges delta and Tripura in the north to Thandwe in the south.

The king himself led the army while he appointed his eldest son and heir-apparent Prince Khamaung to lead the naval fleet consisted of 300 war boats.

The army crossed the Rakhine Yoma range through the passes toward Pegu while the navy went around Cape Negrais toward the key port of Syriam (Thanlyin), which it seized in March 1599 (Tabaung 960 ME).

At Syriam, Razagyi assigned De Brito, the leader of Portuguese mercenaries in his navy, to lead the garrison, and returned home by sea.

In 1609, one of the escapees of Dianga, Sebastian Gonzales Tibao came back with 400 well-armed Portuguese and seized the Sandwip island, wiping out over 3000 Afghan pirates there.

At Sandwip, Tibao brazenly broke the alliance, and seized the entire fleet by "the simple expedient of murdering its captains at a council".

Tibao and his crew then began raiding the Arakanese coast, once reaching all the way up the Lemro river and taking away the king's gold and ivory barge.

[4] The king enlarged the Andaw-thein Ordination Hall in order to house a tooth relic of the Buddha he brought back from his pilgrimage to Ceylon, either in 1596 or 1606–1607.