In World War II. It’s not clear that there actually were any. This isn’t always mentioned in histories, but a lot of what Japan did in the Pacific made no sense at all.
For example, the Japanese occupied lots of islands. After their local naval and air forces had been defeated, we only needed a few of those islands for bases. We generally just let the Japanese forces on the islands we didn’t need sit there, usually till the end of the war. Some farmed and fished, some starved.
But island-hopping had important strategic fallout. There was only one way to send any supplies to places like Rabaul – submarines. Of course, they couldn’t carry enough cargo to make any difference – they sure couldn’t feed 100,000 men – but you gotta do something, right? This took most of the Japanese submarine fleet out of the war.