In a departure from its past policy, North Korea was silent Monday as South Korea-U.S. joint military exercises were launched, a move analysts say may possibly reflect its wish to keep alive the flow of dialogue with Seoul. Pyongyang, which escalated tensions and made itself a virtual pariah state by detonating its third atomic device in February, has remained mum on the Ulchi Freedom Guardian (UFG) that kicked off earlier in the day for a 12-day run.