Because Dnieper river forms a natural obstacle for any...

Because Dnieper river forms a natural obstacle for any geopolitical forces to cross just as the current battle line at Kherson. By setting the border there neither side could easily move across even if the opponent side is weak as in the case of Ukraine once the power of the Yankees is over. Ukraine can sustain the current front line from Kiev to Donbas again Russia with Yankee support but it will collapse once the support of Yankee is removed.