He was remarkable for his dexterity in gaucho-style duel, wielding a long knife in one hand and using a poncho wrapped around the other arm as a protective measure.
He carried two riding pistols, a sabre, and a large knife in a leather sheath for his personal protection, and was assisted by a County Tipperary-born gaucho known as 'Don Eduardo'.
Peter Campbell played a prominent role in the affairs of Corrientes province, and for a period after 1819 acted as its deputy governor.
Between January and March 1819, together with the land forces of governor López, Campbell besieged the town of Capilla del Rosario.
However, in the final naval battle against Monteverde on 30 July 1820, Artigas was defeated by Ramírez, a rival warlord from Entre Ríos province.
The dictator Francia, instead of putting his former foe to death, spared Campbell's life, possibly out of respect for his adversary's courage and military prowess.