Upvote:14
Macau was a Portuguese Colony right next door to Hong Kong. Why didn't Japan invade it during WW2?
Because they didn't need to.
The Portuguese were steadfastly neutral. They weren't a military threat. Macau had no real military value and the authorities there were cooperating. Why spend the resources to invade and occupy an already compliant port and risk adding another country to your already long list of enemies?
However, by the end of 1943, Macau was effectively a Japanese puppet state. Japanese "advisors" took over under threat of occupation.
Japan did invade Hong Kong, and they did invade Portuguese Timor too.
...after the Allies occupied it.
Timor was a key Allied air link to the Philippines, occupying it would harm the Allied defend there, and add to the Japanese defense ring.
The Allies on Dutch Timor were worried about leaving neutral Portuguese Timor weakly defended. Japan could invade and attack on a new flank. So on Dec 17, 1941 they sent over a small force (but larger than the Portuguese garrison) to defend the territory.
Up to this point, the government of Portugal had declined to co-operate with the Allies, relying on its claim of neutrality and plans to send an 800-strong force from Mozambique to defend the territory in the event of any Japanese invasion. However, this refusal left the Allied flank severely exposed, and a 400-man combined Dutch-Australian force subsequently occupied Portuguese Timor on 17 December.
After the necessary protests, the Portuguese agreed to send a stronger defense force if the Allies would leave. This new force sailed from Mozambique on January 28, 1942, but the Japanese invaded before it arrived. The Japanese couldn't leave an Allied force on their flank, and it was the perfect excuse to take the whole island, so they invaded both halves of the island. Initially the Japanese promised that Portuguese neutrality would be respected and they would leave as soon as the battle was over, but they didn't.