Syrian enemies did not have nearly the level of anti-aircraft (and more incoming from NATO countries) that Ukrainians have. I think they are just trying to keep

Syrian enemies did not have nearly the level of anti-aircraft (and more incoming from NATO countries) that Ukrainians have. I think they are just trying to keep irreplaceable fighters and bombers intact at the cost of ground forces. Russia know that in a war of attrition they can outlast Ukraine although it will cost them more than they thought now. I think they gambled based on what happened in Crimea and the "contested" regions of Ukraine.