<p>FORWARD OPERATING BASE ST. MERE EGLISE, Iraq — For two nights in a row, the enemy — whoever that might be — varied his pattern and mortared and rocketed U.S. Army bases here in the Sunni Triangle west of Baghdad shortly after the sun went down, about 6:30 p.m. The enemy’s habit had been to wait until 8 p.m. or so. But despite the change in pattern, on both nights, artillery rounds from two of the six tubes of M119A2 105mm howitzers based here answered, in both cases, getting rounds off in less than five minutes.</p>