On 4 September 1939, the United Party caucus refused to accept Hertzog 's stance of neutrality in World War II and deposed him in favour of Smuts. Upon becoming Prime Minister, Smuts declared South Africa officially at war with Germany and the Axis. He immediately set about fortifying South Africa against any possible German sea invasion because of South Africa 's global strategic importance controlling the long sea route around the Cape of Good Hope.
when did south africa declare war on germany
September 1939