FILE -- In this Sunday, Oct. 2, 2016 file photo, tribesmen loyal to Houthi rebels hold their weapons as they chant slogans during a gathering aimed at mobilizing more fighters into battlefronts in several Yemeni cities, in Sanaa, Yemen. Yemen's civil war is threatening to further entangle the United States in it as American forces have fired missiles into the country in retaliation for attacks launched from Shiite rebel territory. The retaliatory strike comes as America has tried to back away from a Saudi-led military campaign in the country over civilian casualties caused by its airstrikes. (AP Photo/Hani Mohammed, File)
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