TABARRE, Haiti — When a bloody gang war erupted in a busy business district east of Haiti’s capital not far from the U.S. Embassy, Haitian police officers were forced to mount a military-style assault just to reclaim one intersection. Armed with rifles and bulletproof vests, they marched in behind a bulldozer, clearing tires, wooden tables and even an overturned trailer used by the gangs to block the road. But weeks later, holding the ground is a strenuous effort. On a recent weekday, three officers in the specialized Motorized Intervention Brigade, or BIM, joined regular officers in checking …