Which film technique is the film theoretic Sergei Eisenstein said to be the father of?

Explanation

The Soviet theatre and film director and film theorist Sergej Mikhajlovitj Eistenstein (1898 - 1948) is often considered to be the "Father of Montage". He is noted in particular for his silent films such as "Strike" (1924) and "Alexander Nevsky" (1938). He started his career in Moscow, but later on travelled around Europe for two years, giving lectures. In 1930, he was offered an opportunity to go to the US, but he returned to the Soviet Union two years later, where he spent some time in a mental hospital. His film "Ivan The Terrible, Part I" presenting Ivan IV of Russia as a national hero, won Joseph Stalin's approval.