Before this period, the Nationalists had already become dominant, yet the outcome of the war was still not certain. This progressively changed as the Nationalist forces notched up several victories.
The December 1937 – February 1938 Battle of Teruel was an important confrontation between Nationalists and Republicans. The city belonged to the Republicans at the beginning of the battle, but the Nationalists conquered it in January. The Republican government launched an offensive and recovered the city, however, the Nationalists conquered it for good by 22 February. On 14 April 1938, the Nationalists broke through to the Mediterranean Sea during the Aragon Offensive, cutting the government-held portion of Spain in two.