If the global military were a country, it would be the fourth biggest emitter in the world, ahead of Russia.
NATO member states, for example, already spend 17 times as much on the military as Russia.
Adding solar panels to a military base is easy to do, but does nothing to tackle the main challenge, which is fossil fuel consumption by military jets, ships and tanks. For now, there is no alternative, green fuel that can be produced at the scale needed and without triggering unacceptable social and environmental consequences
Ukraine could alzo stop the war right now by entering peace negotiations and giving up the regions which voted for independence. NATO could also end the war by stopping to send weapons to Ukraine.
Yes, all kinds of statements are sort of true even if absurd. E.g. CCCP could defuse the South Sea situation by stopping resistance and finally capitulating to the Republic of China (also known as Taiwan).
Like you say, absurd. China has no reason to stop its resistance to imperial conquest without any fight.