The feast of Our Lady, Help of Christians, was instituted by Pope Pius VII. By order of Napoleon I of France, Pius VII was arrested on June 5, 1808, and detained a prisoner first at Grenoble, and then at Fontainebleau. In January 1814, after the battle of Leipzig, he was brought back to Savona and set free on March 17, on the eve of the feast of Our Lady of Mercy, the Patroness of Savona. The journey to Rome was a veritable triumphal march. The pontiff, attributing the victory of the Church after so much agony and distress to the Blessed Virgin, visited many of her sanctuaries on the way and crowned her images (e.g., the “Madonna del Monte” at Cesena, “della Misericordia” at Treja, “della Colonne” and “della Tempestà” at Tolentino). The people crowded the streets to catch a glimpse of the venerable pontiff who had so bravely withstood the threats of Napoleon. He entered Rome on May 24, 1814, and was enthusiastically welcomed. To commemorate his own sufferings and those of the Church during his exile Pope Pius VII extended the feast of the Seven Dolours of Mary to the universal Church on September 18, 1814.
When Napoleon left Elba and returned to Paris, Murat was about to march through the Papal States from Naples; Pius VII fled to Savona 22 March 1815. After the Congress of Vienna and the battle of Waterloo, the Pope returned to Rome on July 7, 1815. To give thanks to God and Our Lady, on 15 September 1815 he declared 24 May, the anniversary of his first return, to be henceforth the feast of Our Lady, Help of Christians; the 1913 Catholic Encyclopaedia article commented that it has spread nearly over the entire Latin Church, but is not contained in the universal calendar.
Vatican II, in the Constitution on the Church (sections 61, 62), cites this title of Mary, placing it in the context of Mary’s maternal role. “In an utterly singular way she co-operated by her obedience, faith, hope and burning charity in the Saviour’s work of restoring supernatural life to souls. For this reason she is a mother to us in the order of grace…By her maternal charity, Mary cares for the brethren of her Son who still wander through this world in the midst of dangers and difficulties until they are led to the happiness of their heavenly home”.