連合軍は春に大規模な反攻を開始した。
The Allied forces launched a large-scale counteroffensive in the spring.
敵の反攻に備えて、陣地の守りを固めた。
They strengthened the defenses of their position in preparation for the enemy's counteroffensive.
劣勢だった軍は援軍を得て一気に反攻した。
Having received reinforcements, the army that had been losing went over to the attack all at once.