"Balls" have little to do with it. It looks to me like the invasion of Ukraine was the act of a desperate old man whose time is running out to achieve his ambitions, and a mistake based on wishful thinking rather than a sober assessment of relative military capability and popular sentiment of the two countries. This is not a man you can trust to be rational. We should assume he will continue to act out of pride and delusion. If he thinks he doesn't have anything left to lose, we should assume nukes are on the table.