In any military campaign, geography is key. Ukraine shares a 1,900-kilometer (1,200-mile) border with Russia. Ninety percent of Ukraine is flat terrain, punctuated with small hills, depressions and shallow riverine valleys. It is excellent ground for armored warfare, and Ukraine's border is not anchored to any specific or defensible geographic feature. Ukraine's Political Divisions The Dnieper River is a key terrain feature, sloping from the north of Ukraine into the southeast before switching back west of Crimea to the Black Sea. The river effectively bisects the country into its eastern and western regions. The Dnieper River Valley has a well-developed network of ravines and gullies, extending into a system of tributaries. The terrain in eastern Ukraine is predominantly steppe (Ukraine's grasslands, mainly in the south) or forest-steppe (historically broadleaf forests and grassland in a band across Ukraine's center). This provides very good observation across the flatlands.