Summary: U.S. officials are concerned that Islamic extremists may try to exploit Egypt’s upheaval but are not yet convinced that the Muslim Brotherhood, the country’s most influential Islamist opposition group, is necessarily a threat. … One-year retrospective: One year ago today, on February 13, 2010, Aubrey Immelman reported that bombs and booby traps slowed the advance of thousands of U.S. Marines and Afghan soldiers moving through the Taliban-controlled town of Marjah — NATO’s most ambitious effort yet to break the militants’ grip over their southern Afghanistan heartland. NATO said two of its troops were killed in the first day of the operation — one American and one Briton. Afghan authorities said at least 20 insurgents were killed.