There are some interesting parallels between the ongoing conflict in the Ukraine and the Spanish Civil War. It's far from a replay, but nevertheless interesting (to me).
Back in Spain during the 1930's, new equipment was introduced to warfare, although they were mostly incremental improvements of First World War arms: Tanks, monoplane fighters, monoplane bombers with proper bombsights, dive bombers, heavy anti-air guns with elaborate fire control, light rapid fire anti-air guns, anti-tank guns, miniaturized radio sets (and especially the new voice-over-radio mode).
Some lessons were drawn from their use, both wrong and correct ones.
The incorrect ones were drawn because the conflict was not representative of the coming Second World War. The Spanish Civil War was mostly static, but not as much a trench war as the First World War on the Western and Italian fronts due to a shortage of artillery ammunition. It had its mobile phases, but these were reminiscent of the 'successful' offensives of late 1917 and 1918. The focused operational advances of fully motorized forces with tanks had but one disastrous parallel in Spain.
The combat in the Ukraine appears to be similar to what was known from Yugoslavia and Spain; lots of volunteer formations in service (I'm thinking of the Ukrainian side here), very little movement. Seemingly spectacular advances as the recent (possibly intentionally incomplete) encirclement of Debalzewe took weeks, while an action of this size would have been a day's work during 1939-1945.
The Russians may probably not draw many wrong lessons from this since they had similar actions in Chechnya already and employ mostly 1980's technology. Meanwhile, the West might draw some wrong conclusions, albeit the very small involvement will likely diminish this. It's mostly the effects of ammunitions such as (somewhat) modern artillery that may offer good insights for military forces in the EU. The Russian breakthrough day during the South Ossetia War is more worthy of study in regard to mobile warfare.