Prince Harry’s claim in his new book that he killed 25 Taliban fighters during his military service in Afghanistan is drawing extensive pushback from veterans, who say publishing a head count is violating an unspoken code and could jeopardize security for the British forces as well as himself. Retired British Army Col. Tim Collins, who led troops in battle during the March 2003 invasion of Iraq, was harshly critical of the claim. “This is not how we behave in the army. It’s not how we think,” Col. Collins said in an interview with the Forces News British military news organizations....