Russian and Ukrainian officials held a second day of US-brokered talks aimed at ending Moscow’s all-out war on Ukraine, as negotiators grappled with major sticking points about Ukrainian territory and security guarantees. In a small sign of progress, the two sides agreed to another exchange of prisoners of war, something that has happened periodically over the course of the nearly four-year-old Russian invasion. Steve Witkoff, the White House envoy who has led the US-led talks, said on February 5 that 314 prisoners in all would be released.…