[2][3] As his mother spent much time in the company of Peter the Great, rumours suggested that the young Rumyantsev was the monarch's illegitimate son.

In 1761 he besieged and took the Pomeranian fortress of Kolberg,[12][13] which had twice been unsuccessfully beleaguered by other Russia's commanders; thus clearing for Russian armies the path to Berlin.

Here Rumyantsev pioneered a new tactic — the action of troops in battalion (regimental) columns, combined with a scattered formation of jaegers.

In this post, which his father had held with so much honesty, Rumyantsev made it his priority to eliminate any autonomy of the hetmans and to fully incorporate the newly conquered territories into the Russian Empire.

When his forces approached Shumla in 1774, the new Sultan Abdul Hamid I started to panic and sued for peace, which Rumyanstev signed upon a military tambourine at the village of Küçük Kaynarca.

In times of peace, Rumyantsev expressed his innovative views on the martial art in the Instructions (1761), Customs of Military Service (1770), and the Thoughts (1777).

Under his son Sergey's administration, Tashan fell into ruins, although he erected a mausoleum near Balashikha for his father's reburial (which never took place).