The warplanes, a mix of at least 14 MiG-29 fighters and Su-24 fighter-bombers, appear to have taken off from a base in Russia sometime in the middle of May and flown to Hmeimeem, Russia’s airbase on Syria’s Mediterranean coast. There they were repainted, their Russian Federation Air Force markings obscured, before flying more than 1,200 miles and landing in eastern Libya, in territories controlled by Russia’s ally, strongman-in-waiting Khalifa Haftar. The deployment, which the Pentagon revealed last week and Moscow denied, is the latest in a series of escalations that have seen all types of weapons — Turkish and Emirati...