The flatland where Ukraine resides has historically been the region where the most successful invasions of Russia took place. It’s prime strategic territory without any natural barriers, mountains, swamps etc. It’s important for Russia to control Ukraine militarily, and not let them drift into NATO’s sphere of influence.Doesn't make sense imo, Crimea was about access to the sea, about acquiring ports and stationing a fleet. Everyone knew what were the objectives, and Russia suffered a lot due to sanctions. I don't see the benefits to taking the entire country