1.The last time it was the Burmese commander of Arakan, Gen Bandoola who had felt so cocky. In Jan 1824 he marched from Arakan with 60,000 troops with his objective of capturing Calcuatta. King Bodawphaya had instructed the Gen to deliver the Governor General to him alive so that he could torture him to death.
2. The Burmese had miscalculated thinking the English would be tired after their protracted war with the Marathas. However, the Company had in the meanwhile raised ALI ( The Arakan Light Infantry). ALI was raised as a regiment of the Bengal Presidency Army with exiled Arakanese and some Monipuris. With ALI to spearhead their advance the completely mauled Bandoola's army causing huge casualty. Bandoola was among the dead.
3. It is interesting that after loosing the First Anglo Burma War, the Burmese king had no objection in signing away Arakan to the English. Similarly after the Second War more territory was signed away. However, after loosing the Third War King Thebaw flatly refused to sign away the Burman heartland. He said he could sign away what they had usurped from others but he had no authority to sign away core Burma itself. The GG therefore had to annex Burma through a proclamation.
4. In Suu Kyi's famous book The Freedom from Fear, she accepts candidly that whenever Burmans were strong they occupied surrounding territories. Again when weakened they withdrew into core Burma.