The European Union was founded on the principles to prevent war. The war in the Ukraine was needless and should have been prevented

Indeed. It is a shame that the European Union has never, until these past couple of weeks, given itself the means to have any serious influence in defence matters.

If you recall, Putin was crystal clear from the start, that he wanted to negotiate with Biden and nobody else : the master of Nato.

So, hypothetically, they might have negotiated. Given that Putin's non-negotiable conditions included the disarming of the front-line NATO states, that would have needed a formal decision by all of the NATO member governments. The hypothesis that the USA decides everything in NATO would have been tested, and found to be false, because there is not the slightest chance that the front-line states would have accepted to disarm.

So from that point of view, no, the war could not have been prevented, and Putin knew it perfectly.

His only miscalculation was thinking that he could win the war he had already decided to launch, and that this would give him a strategic advantage. Instead, he has plunged Russia into decades of torment (Ukraine will recover much quicker)

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}