In 1935, the Italian invasion of Ethiopia prompted some soul-searching about the defence of the British territories in the vicinity. The Sudan was the missing 'bridge' between Italian East Africa and Italian North Africa, so the issue was taken very seriously in Khartoum. Accordingly, some young SPS were allowed join the reserve of the Sudan Defence Force (SDF). This was to prove useful when the war did break out later, as most administrators had to remain in post for some time, until older men could be recalled to replace them.