Could annexing parts of Ukraine lead to an escalation of the war?

Russian President Vladimir Putin has announced the country's first partial military mobilization since World War II, with some 300,000 reservists expected to be initially called up. Why the mobilization now? Dialogue also covers another topic: Global leaders convened in New York this week for the 77th session of the UN General Assembly. How has the Ukraine crisis been discussed? How have countries been affected by the crisis?