Things look a bit more complex than the parent and OP make it. The first one on Kiska island resulted from Canadian and American detachment taking each other for the enemy. Agreed this is friendly fire - but among sub-optimally coordinated detachment - not within on single force.
The second one on Woodlark and Kiriwina which had less casualties was not only unopposed, it was known to be unopposed, so expectations were differnt.
The other opposed landings are more difficult to read.
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