Assuming this refers to the resolution of the Time War, no one. The 50th anniversary special "The Day of the Doctor" reveals that the Eleventh Doctor, in conjunction with all his previous incarnations (plus a future self), execute a plan to place Gallifrey in a pocket universe. Although the planet is technically lost, its population - particularly its billions of children - survive. Unfortunately, due to changes occurring in the time lines, the War Doctor and Tenth Doctor, who helped formulate the plan with the Eleventh - are unable to remember this, so the War Doctor regenerates into the Ninth Doctor believing he killed all the Time Lords. It is not until his Eleventh incarnation arrives at the point in time where the plan is executed that he remembers that he didn't kill them after all.