Yerevan, Armenia — The separatist government of Nagorno-Karabakh said Thursday it will dissolve itself and the unrecognized republic will cease to exist by year’s end after a three-decade bid for independence, while Armenian officials said over half of the region’s population has already fled. The moves came after Azerbaijan carried out a lightning offensive last week to reclaim full control over the breakaway region and demanded that Armenian troops in Nagorno-Karabakh disarm and the separatist government disband. A decree signed by the region’s separatist President Samvel Shakhramanyan cited a Sept. 20 agreement to end the fighting under which Azerbaijan will allow the “free, voluntary and unhindered movement” of Nagorno-Karabakh residents to Armenia.