Comment by api

Look at how fast various nations ramped up advanced (for the time) military production before and during WWII, or the Manhattan Project, or the Apollo program, or China's rapid rise.

Engineers who know how to build factories, batteries, and solar panels could sit down and create a "war plan" to build out and scale infrastructure quickly if you asked them to do it and then got out of the way.

The EU has plenty of talent with the know-how to do this. If it couldn't be done even in a crisis situation, that's a political problem.