Toungoo – Hanthawaddy War ( 1534 – 41 ) The Toungoo – Hanthawaddy War ( 1534 – 1541 ) ( ) was a military conflict between Toungoo Kingdom , and the Hanthawaddy Kingdom and its allies the Prome Kingdom and the Confederation of Shan States that took place in present - day Lower Burma ( Myanmar ) between 1534 and 1541 . In a series of improbable events , the upstart Burmese - speaking kingdom defeated Mon - speaking Hanthawaddy , the most prosperous and powerful of all post - Pagan kingdoms before the war . In the following years , Toungoo used the newly acquired kingdom ' s wealth and manpower to reunify the various petty states that had existed since the fall of Pagan Empire in 1287 . Background . Since its founding in 1279 as an outpost of Pagan Kingdom , Toungoo , located in remote , hard - to - reach corner east of the Pegu Yoma ( Bago Yoma ) range , had always been a troublesome province for its overlord . During the Ava period , its governors and viceroys raised multiple rebellions ( 1427 – 1428 , 1437 – 1442 , 1451 – 1458 and 1468 – 1470 ) , each time with clandestine or open help from Hanthawaddy , which wanted to keep Ava unstable . Ironically , Toungoo would repay by attacking Hanthawaddy itself . Circa 1494 , Toungoo , then still a vassal of Ava , raided Hanthawaddy ' s territory , taking advantage of the larger kingdom ' s succession crisis . But Hanthawaddy ' s new king Binnya Ran II retaliated by laying siege to Toungoo itself in 1495 – 1496 . Toungoo barely survived the siege ; Mingyinyo , viceroy of Toungoo , would not provoke the larger neighbor for the remainder of his life . After he declared independence from Ava in 1510 , Mingyinyo largely stayed out of the fighting raging between Ava and the Confederation of Shan States . When Ava fell to the combined forces of the Confederation and Prome in 1527 , many people fled to Toungoo , the only region in Upper Burma at peace . But Toungoo could not stay out of the warfare forever . War arrived uncomfortably close to Toungoo in 1532 – 1533 when the Confederation of Shan States , already ruling much of Upper Burma , attacked its erstwhile ally Prome , and sacked the city . Although the Confederation was content to keep Prome as a vassal , the Toungoo leadership was concerned that their city east of Prome on the same latitude , separated only by the Pegu Yoma range , was an " obvious next target . " Fortunately for Toungoo , the Confederation was distracted by the leadership change after its principal leader Sawlon of Mohnyin was assassinated in 1533 . Moreover , Toungoo ' s remote hard - to - reach location proved an asset . Unlike Prome , which sits on the Irrawaddy river , Toungoo was tucked away behind the Pegu Yoma range and was not connected to Upper Burma by any major water way , presenting a difficult logistical challenge for potential invaders . Meanwhile , refugees continued to flee to Toungoo , still the only kingdom unaffected by war . The little principality now commanded considerably more manpower than its traditional base allowed for , and it would soon punch above its weight . The Toungoo leadership decided that their kingdom " had to act quickly if it wished to avoid being swallowed up " by the confederation . Tabinshwehti and his court selected Hanthawaddy as their first target because its king Takayutpi was a weak leader who did not command respect of his vassals . Takayutpi ' s brother - in - law Saw Binnya practically ruled Martaban region like a sovereign , and scarcely acknowledged the high king at Pegu ( Bago ) . Takayutpi in turned made an alliance with the Prome Kingdom , a vassal of the Confederation . Initial raids ( 1534 – 1537 ) . The war began in late 1534 when a landlocked Toungoo led by Tabinshwehti and his deputy Bayinnaung , tried to break out of its increasingly narrow zone by launching a preemptive war against a weakly led Hanthawaddy . In the beginning , Toungoo ' s maneuvers amounted to a mere raids of Hanthawaddy territory , and its initial dry - season raids in 1534 – 1535 , 1535 – 1536 , and 1536 – 1537 all failed against Pegu ' s fortified defenses aided by foreign mercenaries and firearms . In each campaign , Toungoo armies had only 6000 to 7000 men , a few hundred cavalry and a few dozen war elephants and did not yet have access to foreign troops and firearms . Unlike his father Binnya Ran II , King Takayutpi of Hanthawaddy could not organize any retaliatory action . His nominal subordinates in the Irrawaddy delta and Martaban did not send any help . Nonetheless , Pegu ' s defenses led by two leading ministers of the court , Binnya Law and Binnya Kyan withstood the raids . Coup de grace ( 1538 – 1539 ) . Pegu . Toungoo used a stratagem to create a split in the Hanthawaddy camp , providing misinformation about the loyalty of the ministers . Surprisingly , Takayutpi believed Toungoo ' s misinformation , and executed the ministers who had been his tutors since childhood and were absolutely devoted to him . Then when Toungoo launched another invasion in late 1538 , with 7000 troops , Takayutpi was helpless , and decided to evacuate his capital rather than fight . Toungoo forces took Pegu without firing a shot . The most telling part of the state of disarray of the once powerful kingdom was that Takayutpi and his armies chose to retreat to Prome , another kingdom , rather than to their own territory of Martaban whose ruler Takayutpi simply did not trust . The course of retreat was through the Irrawaddy delta . The direct route from Pegu to Prome , though much shorter , involved crossing the Bago Yoma range , and was not practical for large armies . Takayutpi divided the retreating Hanthawaddy forces into two . Five divisions of the army marched by land . Takayutpi and the remaining troops sailed by river in 700 boats . Battle of Naungyo . At Pegu , Tabinshwehti and his deputy Bayinnaung well understood that they had gained Pegu only through a ruse , and that Hanthawaddy ' s military had not been defeated yet . Their top priority was to meet and defeat the Hanthawaddy army before they got inside the fortified walls of Prome . They knew that a large body of enemy inside walls with better leadership would pose a major problem for their tenuous hold on Lower Burma . Tabinshwehti sent Bayinnaung with a small army to chase the retreating army while he sailed up to Prome with his flotilla of war boats to chase Takayutpi ' s flotilla . Bayinnaung ' s light troops caught up with the main Hanthawaddy armies led by Gen . Binnya Dala and Gen . Minye Aung Naing near Naungyo in the Irrawaddy delta . Bayinnaung nonetheless defeated the numerically superior and better armed force . Only a small portion of the Hanthawaddy forces made it to Prome . A decimated Hanthawaddy was no longer in a position to retake the lost territories from Toungoo . Battle of Prome . After Pegu ' s improbable fall , the Shan Confederation , which ruled the former Ava Kingdom , finally took notice . When Toungoo ' s armies later attacked its vassal Prome , the Confederation sent in troops and broke the siege . Toungoo retreated but soon gained the allegiance of many Mon lords , and manpower after Hanthawaddy ' s king Takayutpi died a few months later . Martaban ( 1540 – 1541 ) . Preparations . Toungoo now held two out of the three Hanthawaddy provinces ( the Irrawaddy delta and Pegu ) but Martaban remained independent . The viceroy of Martaban , who had always acted like a sovereign , had declared himself king of Hanthawaddy since the death of Takayutpi . Tabinshwehti sent an ultimatum to Martaban and its vassals to submit in exchange for amnesty but Saw Binnya refused . He had fortified the wealthy port , and enlisted Portuguese mercenaries and seven warships led by Paulo de Seixas , guarded the harbor . Martaban ' s vassals wavered . The governor of Moulmein did not submit to Tabinshwehti but agreed not to provide any help to Martaban . Siege . In November 1540 , 13 , 000 - strong Toungoo land and naval forces attacked the city . Toungoo forces now included 700 Portuguese mercenaries led by João Caeiro ( Joano Cayeyro ) who brought light artillery and muskets . However , the wealthy port ' s strong fortifications backed by Portuguese artillery and musket fire kept besiegers at bay . Toungoo ' s light Portuguese artillery proved " useless against ramparts backed by earthwork , " and its " navy " of small war boats could not impose a complete blockade on the seven Portuguese ships guarding the harbor . The Toungoo command tried to complete the blockade about a month into the siege by sending in 300 war boats to storm the harbor but the venture ended badly , with most boats destroyed by the guns of the Portuguese ships . For the next few months , Toungoo forces continued the siege from afar but the Toungoo command was concerned by the fast approaching rainy season . Even though the first naval attack failed , Adm . Smim Payu convinced Tabinshwehti , who was personally leading the siege , that their best chance for a breakthrough still lay in another naval attack . The king accepted the plan . The admiral went up the Salween river with thousands of men , and built two types of rafts . One type contained bamboo towers higher than the walls of the port . The others were fire - rafts . While Toungoo forces prepared for the final assault , the city was starving . Saw Binnya finally offered to surrender provided that he be allowed to remain viceroy in exchange for an annual tribute of 30 , 000 viss ( 48 , 987 . 9 kg ) of silver bullion and other valuable presents . Tabinshwehti rejected the offer , demanding an unconditional surrender instead . Saw Binnya then asked for safe - conduct out of the city for himself and his entire family , together with his treasures . It too was rejected by the Burmese king . In desperation , Saw Binnya appealed to the Portuguese viceroy at Goa for assistance , offering to become a vassal of Goa , in addition to an outright gift of half the amount of his treasure . The Portuguese were interested . A Portuguese captain listed the treasure as consisting of two shiploads of gold and silver , and 26 chests of precious stones . In addition , gold to be looted from the city ' s pagodas would fill 4 ships . But the Portuguese also feared the vengeance of Tabinshwehti , the new power in Lower Burma , and " wavered between greed and prudence " . At the same time , Saw Binnya offered a large bribe to Caeiro to help him and his family escape . Caeiro seriously considered the overly generous offer but ultimately declined the offer as his deputies found out the proposal and threatened to report the matter to Tabinshwehti . Final assault . While Saw Binnya was exhausting all his options , the Toungoo command was determined to sack the city before the rainy season . In May 1541 , seven months into the siege , Smim Payu launched the second attack on the harbor . Several fire - rafts " with flames higher than a toddy tree " came floating down the river toward the Portuguese ships . Three of the seven Portuguese ships fled to the sea . The remaining four ships were either burned or captured . Then the rafts with mounted bamboo towers , crammed with troops and musketeers , slipped past the wreckage , and made it to the wall by the harbor . The Toungoo troops , who were exchanging musket fire with the defenders on the wall , then jumped over the wall and soon won a foothold . A section of the wall was mined and brought down . Inside the city , the defenders fought on , with Saw Binnya personally leading the fight on his war elephant . But they were soon overwhelmed . The sack raged for three days . Tabinshwehti ordered the execution of the viceroy , his family , and all the " gallant " defenders for they had refused his prior offer of amnesty . The mass execution had the desired effect . The governors of Moulmein ( Mawlaymyaing ) and southern territories ( present - day Mon State ) , abutting then Siamese frontier submitted . Significance . The war was a crucial turning point in the history of Myanmar as well as in the history of mainland Southeast Asia . Toungoo ' s victory gave the upstart kingdom complete control of coastal Lower Burma ' s manpower , access to foreign firearms and maritime wealth to pay for them . Toungoo kings would leverage these new found assets for further expansions in the remainder of the century , and build the largest empire in the history of Southeast Asia . Moreover , Toungoo ' s success in breaking out of an increasingly narrow dry zone not only saved the only remaining ethnic Burman - led kingdom from extinction but also ensured the continued rise of Burman culture and Burmese language in the Irrawaddy valley .