The Argentinian force originally occupying Mount Challenger, commanded by Major Ricardo Cordón, consisted of the 4th Infantry Regiment ("Regimiento de Infantería 4" or RI 4) , with the bulk of the defenders drawn from C Company with the 1st Platoon (Sub-Lieutenant Miguel Mosquera-Gutierrez) and 2nd Platoon (Sub-Lieutenant Jorge Pérez-Grandi) on the northern peak of Two Sisters and the 3rd Platoon (Sub-Lieutenant Marcelo Llambias Pravaz) on the southern peak and the 1st Platoon A Company (Sub-Lieutenant Juan Nazer) and Support Platoon (Second Lieutenant Luis Carlos Martella) on the saddle between the two.