"The ukraine" is pre-Soviet, not Soviet. In the Soviet times it was Ukraine, a separate Soviet Socialist Republic with its own and clearly demarcated internal border within the Union, and not just vague and shifting "the borderland" between various empires. It was the very first time Ukraine actually got real borders, and these borders (revised during WWII) are in use to this day. "The" Ukraine, or Cossackdom, would be this pre-Soviet history.