When Russian aircraft bombed a remote garrison in southeastern Syria last month, alarm bells sounded at the Pentagon and the Ministry of Defense in London.

The Russians weren’t bombarding a run-of-the-mill rebel outpost, according to U.S. officials. Their target was a secret base of operations for elite American and British forces. In fact, a contingent of about 20 British special forces had pulled out of the garrison 24 hours earlier. British officials declined to comment.

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