Its surface area — more than 300 square miles — is more than twice that of Washington D.C.’s. “There’s just a lot of terrain [Russia] would need to cover, and Russian combat forces are actually somewhat light on infantry,” said Scott Boston, a senior defense analyst at the Rand Corp.

Kyiv is bisected by the Dnieper River, “like two large cities that can mutually support one another across the river,” Boston said. Ukrainians seized on that geography, destroying bridges near the city. Flooded areas also may have impeded a Russian advance.

Russian forces also failed to quickly capture Antonov Airport, which would have allowed them to establish a base to bring in more equipment and supplies. They eventually captured the area, but by then, they were bogged down with intense battles.