Jacob Magnus Sprengtporten (1721–1786)

J.M. Sprengtporten already took part in the supervision of the fortification works of Sveaborg in the 1750s. Promoted to lieutenant-general, Sprengtporten became Augustin Ehrensvärd’s successor in the beginning of the 1770s. During his term of only 1.5 years, he made the significant decision of discontinuing all fortification works on the side of Helsinki. According to the new fortification plan, Sveaborg would also have to be fortified from the north side, as the attack could come from the mainland as well.

In 1772, J.M. Sprengtporten gathered a group of fortification officers and soldiers in Sveaborg, and sailed with them to Stockholm to support King Gustav III in the coup. Gustav III intended to force the classes to surrender power to the king. However, the coup was already over when the ship, delayed by the autumn storms, reached Stockholm. The task of continuing Ehrensvärd’s work was apparently the king's reward to Sprengtporten for his loyal assistance in the coup.

Jacob Magnus was the half-brother of Georg Magnus Sprengtporten, the first Russian Governor-General of Finland.