“Everyone goes to Valuyki.” That phrase, captured on social media, may have provided the biggest clue about where Russia’s armed forces might strike Ukraine if Russian President Vladimir Putin unleashes the 130,000 troops he has massed along the border.

Draw a straight line from Valuyki, strategically located north of the Russian-backed breakaway Donbas region and east of Kharkiv, to the large city of Dnipro on the river Dnieper. It is approximately 300 kilometers, the shortest possible distance to the formidable natural defense that the river provides. Controlling that line would enable Russia to cut off all of southern and eastern Ukraine, completely encircle the Ukrainian armed forces currently facing Donbas and quickly compel them to surrender.

The immediate military rewards would be significant: complete control of the Sea of Azov and secure defense of the land corridor to annexed Crimea, including of fresh water flowing into the rain-starved peninsula. And if Ukrainian military resistance is unexpectedly weak, Russia could extend its land-grab beyond Odessa to the Moldovan border, cut off Ukraine’s access to the Black Sea altogether and cripple its maritime economy.