I don't think the red is used correctly here.

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On December 8, 1941, the Japanese made an amphibious landing on the coast of Thailand, part of the comprehensive sweep of South Pacific islands that followed the bombing raid at Pearl Harbor, Hawaii. The Japanese had assistance, though: Thailand's prime minister, Lang Pipul, collaborated with the Japanese, embracing the Axis power's war goal of usurping territory in China and ruling over the South Pacific. Pipul wanted to partake in the spoils; toward that end, he declared war on the United States and England. In October, he took dictatorial control of Thailand and became a loyal puppet of the Japanese.

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Adam is correct. This usage of "though" is very similar to using "however" in the same context.

Thank you so much , but I am still puzzled and didn't understand it at all.
the word is resistance not assistance

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And October here is not so clear, Oct 1942 or 1943?