Italian invasion of British Somaliland
This campaign in Somali Coast Protectorate was like all the others of the Axis: it initially started with a victory, then after a period of time (like the campaigns in the Balkans, in the Philippines or in Russia), finished with a complete defeat. But in the specific case of the Italian conquest of British Somali Coast Protectorate, the defeat (that happened in spring 1941) was followed by nearly two years of Italian guerrilla war in Ethiopia.