 The Republicans then counterattacked twice with Soviet tanks, which were beaten off with artillery fire from Nationalist batteries dug in on "La Marañosa", but they served to hold up further Nationalist advances.When Junkers of the Condor Legion appeared overhead in support of the Nationalists, Republican planes shot them down and took control of the skies.Until February 13, the Republican air force, largely composed of Soviet machines and pilots, maintained air supremacy.