The Ukrainian People's Republic was formed after the Russian Revolution of 1917, and lasted until the Peace of Riga between Poland and Soviet Russia in March 1921.
The Directorate of Ukraine was a provisional council of the UNR formed after Skoropadskyi's Hetmanate fell apart.
This regime was deposed in December same year, when the Ukrainian People's Republic was reinstalled, now led by the Directory.
In mid July 1918 there were some biases about the idea of the Ukrainian SSR, but with the help of more nationally inclined bolsheviks such as Skrypnyk, Zatonsky, and others the government of the Soviet Ukraine was preserved.
After the defeat of Directoria the head of state was again called as the chairman of the Central Executive Committee.