During the 18th century, the Ashanti became the ascendant nation in the region of the Volta River, or modern day Ghana and extending west into present day Ivory Coast. Access to the coast and control of coastal trade was a source of continued conflict with the Fanti city states along the coast. Eventually the Ashantis became so powerful that they raided coastal towns and forts. At this point, the British needed to either protect the Fanti tribes with whom they traded from being massacred and enslaved by the Ashanti, or leave them to their fate. There was added pressure to effectively end the slave trade, which was a large source of revenue for Ashanti who had an extremely large prisoner of war population, which was now overwhelming the local population in the capital, Kumasi.
The British vacillated for years on the best course of action and eventually stumbled into the First Ashanti War in 1823.
In 1824, the British, led by Charles McCarthy, were squaring up for a dreadful conflict with the Ashanti. McCarthy, with some arrogance or bad military intelligence, led his army of barely 600 men against perhaps 10,000 Ashanti warriors and their king, Osei Tutu Kwadwo. (The exact numbers are very hard to pin down.)
McCarthy's planning was bad and therefore so was his logistical supply in mostly swamp and jungle conditions with seemingly ceaseless downpours. Little wonder that his men were demoralized and exhausted. Moreover, after the first skirmish the British had all but run out of ammunition.
So confident was the king of the Ashantis that he prophesized that soon he would defeat the British and that McCarthy's jawbones would be used as drumsticks and his skull as a loving cup. As the Ashanti advanced, Sir Charles ordered his band to strike up with God Save the Queen.
The closer the Ashanti got, the quicker McCarthy's Fantis deserted him. When the British guns were silent the Ashanti held back thinking the silence was a British ploy. But then it dawned. The British had run out of musket balls and powder. As one of the few survivors reported "our gallant little force still defended themselves with their bayonets until they were completely over-powered by the myriads who instantly beheaded nearly every one of those who unfortunately fell into their remorseless hands". McCarthy was killed on January 21, 1824 at what came to be known as the Battle of Nsamankow, near present day Bonsaso. The Ashanti's famously used the governor's skull and those of others as drinking cups, which did not endear them to the British.
It was not until 1831 that a treaty was signed to define the boundaries of the Ashanti kingdom and the authority of the British territorial claim in the Gold Coast.