Battle of Nsamankow

In late 1823, following the disagreements between the Fantis and the Ashantis, he declared war on the king of the Ashanti; after organising the defences of Cape Coast, he set out with an expedition of some 80 men of the Royal African Colonial Corps, 170 men of the Cape Coast Militia, and 240 Fanti tribesmen under their local chiefs. He was accompanied by a captain and an ensign of the 2nd West India Regiment, as aides-de-camp, a surgeon of the same regiment, and J. T. Williams, his colonial secretary. This was not the only part of his force; three other groups of infantry were in the region, one of 600 regulars of the RACC and 3,000 native levies, one of 100 regulars and militia and 2,000 levies (under Major Alexander Gordon Laing), and a third of 300 regulars and militia and 6,000 levies. The plan was for the four groups to converge and then engage the enemy with overwhelming force.

On the night of the 20th, still without having joined forces with the other three groups, his force camped by a tributary of the Pra River. The next day, at around 2pm, they encountered a large enemy force of around ten thousand men; in the belief that the Ashanti army contained several disaffected groups whose chiefs were willing to defect, MacCarthy instructed the band to play the National Anthem loudly. The Ashanti responded by approaching closer, beating war drums, and his beliefs were swiftly dispelled.

Fighting started shortly thereafter; the two sides were separated by a 60-foot-wide (18 m) stream, which the Ashanti made no major attempt to ford, both sides contenting themselves with staying firm and keeping up a continual musket fire. However, the British forces were lightly supplied; the bearers bringing the supplies up in the rear, which included most of the gunpowder and ammunition, mostly fled after hearing the firing in the distance and encountering deserters straggling back. Only one additional barrel of powder and one of shot were brought up, and ammunition ran out around 4pm; the Ashanti then made a determined attempt to cross the river, and quickly broke into the camp.

Almost all the British force were killed immediately; only around 20 managed to escape. MacCarthy, along with the ensign and his secretary, attempted to fall back; he was wounded by gunfire, however, and killed by a second shot shortly thereafter. Ensign Wetherell was killed whilst trying to defend MacCarthy's body and Williams taken prisoner. On his return, he related that he had only survived through being recognised by an Ashanti chief for whom he had done a small favour, and was spared; he was held prisoner for several months, locked in a dwelling which he shared with the severed heads of MacCarthy and Wetherell, kept as trophies of war. McCarthy's gold-rimmed skull was later used as a drinking-cup by the Ashanti rulers.