They made a deal years ago, and russia (like trump would) failed to honor it. They gave up their nukes in exchange for a promise they would not be invaded. "The result was the Trilateral Statement, signed in January 1994, under which Ukraine agreed to transfer the nuclear warheads to Russia for elimination. In return, Ukraine received security assurances from the United States, Russia and Britain;"
More here www.brookings.edu
I would not trust anything trump touches.
Mail-in voting? No chance.