Shiite rebels and Sunni militiamen battled in Sanaa for a second day Friday in battles that have killed at least 120 people and have shaken the Yemeni capital with thousands fleeing their homes. Yemen has had years of turmoil and division, particularly a longtime battle with perhaps the most dangerous branch of the al Qaeda terror network, separatist uprisings in the south and political upheaval that overthrew a longtime autocrat, all on top of deep poverty and tribal tensions.