Weismann, according to the accounts of his contemporaries, had great military talent and enjoyed the trust and love of troops; his name was the most popular in Rumyantsev's army.

In 1769, pursuing one of their detachments, Weismann got carried away, crossed the Ottoman border with Russia and burned the city of Balta, now located in modern Ukraine.

[2][1] In the war, Weismann displayed the courage, energy and skill of a military commander, and was promoted to the rank of major general.

Weismann executed this maneuver, defeated at Karasu [ru] an 8,000-strong Turkish detachment observing a course of the river, and then through Hîrșova moved to Gurobal.

However, during its further movement towards Silistra, Weismann had to hand over his division to Stupishin, the senior among the lieutenant generals, and was appointed head of the vanguard.

[2][1] Osman Pasha, who was defending Silistra, tried to delay the Russian movement and with 30,000 troops took a favourable position 5.3 km (3.3 mi) below the fortress.

Weismann held the trenches occupied by him the whole day and cleared them at night on the orders of Rumyantsev, after news come in of Numan Pasha moving with a 20,000-strong corps from Shumen/Shumla to reinforce Silistra.

But his death was noticed by his troops, who fiercely repulsed the Turkish onslaught, drove them from their position and massacred them, giving no mercy even to the prisoners.