In a significant shift, the Marine Corps has replaced a full infantry battalion in Afghanistan with a single company — another sign that a drawdown in forces there is well underway. Third Battalion, 3rd Marines, out of Marine Corps Base Hawaii, returned home over the last week from Helmand province. They’ll hold a ceremony early Thursday to mark the end of its last combat deployment in Iraq and Afghanistan, according to this report. The battalion was replaced in Afghanistan’s Garmser district by Kilo Company, 3rd Battalion, 8th Marines, out of Camp Lejeune, N.C. The district was the site of heavy combat…