Your statement beautifully captures a central theme in Ellen White's writings about Christ's sacrifice and its purpose for our spiritual warfare. Ellen White extensively wrote about how Christ's endurance of the cross provides us with strength to overcome in our battles against Satan and the powers of darkness.
She affirmed this truth powerfully: "Christ has shown that His love was stronger than death. He was accomplishing man's salvation; and although He had the most fearful conflict with the powers of darkness, yet, amid it all, His love grew stronger and stronger. He endured the hiding of His Father's countenance, until He was led to exclaim in the bitterness of His soul: 'My God, My God, why hast Thou forsaken Me?' His arm brought salvation. The price was paid to purchase the redemption of man" (
2T 212.2).
Ellen White emphasized that Christ's victory over Satan makes our victory possible: "Satan assailed Christ with his fiercest and most subtle temptations; but he was repulsed in every conflict. Those battles were fought in our behalf; those victories make it possible for us to conquer. Christ will give strength to all who seek it" (
4SP 330.1).
She also wrote about how Christ's suffering specifically equipped Him to help us in our conflicts: "When temptations and trials rush in upon us, let us go to God, and agonize with him in prayer. He will not turn us away empty; but will give us grace and strength to overcome, and to break the power of the enemy" (
ExV 27.6).
The cross was indeed the decisive battle: "The conflict between Christ and Satan was determined when the Lord arose from the dead, shaking the prison-house of his enemy to its foundations, and robbing him of his spoils" (
3SP 239.2).
Ellen White consistently taught that Christ's endurance of the cross was not just for our forgiveness, but to provide us with the very strength we need to overcome Satan's temptations and the powers of darkness in our daily spiritual battles.