US and German Tanks for the Ukrainians

Inorder to spearhead a spring counter offensive to the East. The Ukrainians need at least 400 tanks (not even counting the strategic doctrine of at least a 100 in reserve) . Ideally divided into four armored and motorised columns comprising of a ratio mix of 1 tank to 4 armored personnel carriers and 4 light fast moving artillery pieces. Two of these columns will project into the salient in Donbass and two configured as the claws of a crab on either side closing fast to encircle the Russians 150 km east of the Dnipro. Every staff officer whose accustomed to planning regularly would know this as an immovable sine quo non of warcraft. So why are the US and Germans only sending less than 50 tanks to the front? What do they hope to accomplish with that miserable number of tanks. At one level of understanding it hardly makes any strategic planning sense at all. Unless one is attempting to forward the proposition the charge of the light brigade is a sensible military plan. But then again which part of the Ukrainian War makes any sense at all?