KANDAHAR, Afghanistan—U.S. spy drones had no trouble spotting the Taliban fighters. There were more than 20 figures snaking through sparsely wooded hills, trying to outflank the Afghan government commandos in the village below.

In the starry darkness overhead, American helicopters loitered armed with precision-guided missiles, along with a flying gunship capable of drenching the area with cannon-fire. It would have been a hard shot to miss.

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