If defensive weapons don't work because too expensive, then the only way out seems to be M.A.D. which Ukraine can only attain if they join NATO.
Not the only way. Sending drones against Russia's oil industry and logistics centres is having a pretty spectacular effect too, and Russia's having no luck defending against those either.
Not the only way. Sending drones against Russia's oil industry and logistics centres is having a pretty spectacular effect too, and Russia's having no luck defending against those either.