Not one of our more spectacular invasions.
In 1884, we were afraid that the Germans might expand their influence into Bechuanaland and link up with the Boers who were opposed to us. Consequently, we sent the Warren Expedition north to assert British control. Major General Charles Warren (later to head the London Metropolitan Police and be criticised for its failure to catch Jack the Ripper) marched north from Cape Town with a force of 4,000 British and local troops, plus the very first three observation balloons that the British Army had ever used in the field. The Warren Expedition turned up and achieved its objective without firing a shot, though presumably not without sending up a balloon.
Botswana became independent on 30 September 1966.