<P> By 1822, Burmese expansion into Manipur and Assam had created a long border between British India and the Burmese Empire . The British, based in Calcutta, supported rebels from Manipur, Assam and Arakan fleeing into British territory . Calcutta unilaterally declared Cachar and Jaintia British protectorates, and sent in troops . Cross border raids into these newly acquired territories from British territories and spheres of influence vexed the Burmese . Convinced that war was inevitable, Burmese commander - in - chief, Maha Bandula, became a main proponent of offensive policy against the British . Bandula was part of the war party at Bagyidaw's court, which also included Queen Me Nu and her brother, the Lord of Salin . Bandula believed that a decisive victory could allow Ava to consolidate its gains in its new western empire in Arakan, Manipur, Assam, Cachar and Jaintia, as well as take over eastern Bengal . </P> <P> In September 1823, the casus belli was Burma occupying Shalpuri Island near Chittagong, which was claimed by the East India Company . </P> <P> In January 1824, Burma sent one of their top generals, Thado Thiri Maha Uzana, into Cachar and Jaintia to disperse the rebels . The British sent in their own force to meet the Burmese in Cachar, resulting in the first clashes between the two . The war formally broke out on 5 March 1824, following border clashes in Arakan . </P> <P> The British reason for the war was, in addition to expanding British Bengal's sphere of influence, the desire for new markets for British manufacturing . The British were also anxious to deny the French the use of Burmese harbours and concerned about French influence at the Court of Ava, as the kingdom was still known to them . British Ambassador Michael Symes's mission was equipped to gain as much knowledge as possible of the country for future British plans whereas previous envoys were concerned principally with trade concessions . Anglo--French rivalry had already played a role during Alaungpaya's endeavours of unifying the kingdom . The Burmese in these wars were advancing into smaller states not ruled by the British or the subject of expansionary goals by the British before the war began, and the British were not so much preoccupied by the refugee problem initially as by the threat posed by the French until further incidents forced their hand . </P>

When did the first anglo burmese war begin