Having learned harsh lessons from the first war, the Russian military, rather than getting entangled in messy urban engagements such as that seen in Grozny in 1994–95, relied heavily on aerial bombardment and artillery such as ballistic missiles and fuel air explosives, typically surrounding and then destroying any towns or villages that put up resistance before sending in ground forces for mop-up operations. The second Battle of Grozny in 1999–2000 saw the bulk of Chechen resistance smashed, particularly after a column of some 2,000 fighters attempted to break out of the besieged city in February 2000 and instead walked directly into a minefield that Russian forces had prepared for an ambush. What remained of the decimated rebel units then withdrew into the inaccessible Vedeno and Argun gorges in the southern mountains of the republic in order to wage a guerrilla campaign.