The magnificent chorale to which the hymn is sung is also Luther's work. Never have words and music been combined to make so tremendous an appeal. Great musical composers have turned to its stirring theme again and again when they have sought to produce a mighty effect. Mendelssohn has used it in the last movement of his Reformation symphony; Meyerbeer uses it to good advantage in his masterpiece, "Les Huguenots"; and Wagner's "Kaisermarsch," written to celebrate the triumphal return of the German troops in 1870, reaches a great climax with the whole orchestra thundering forth the sublime chorale. Bach has woven it into a beautiful cantata, while Raff and Nicolai make use of it in overtures. After Luther's death, when Melanchthon and his friends were compelled to flee from Wittenberg by the approach of the Spanish army, they came to Weimar. As they were entering the city, they heard a little girl singing Luther's great hymn. "Sing on, my child," exclaimed Melanchthon, "thou little knowest how thy song cheers our hearts." When Gustavus Adolphus, the hero king of Sweden, faced Tilly's hosts at the battlefield of Leipzig, Sept. 7, 1631, he led his army in singing "Ein feste Burg." Then shouting, "God is with us," he went into battle. It was a bloody fray. Tilly fell and his army was beaten. When the battle was over, Gustavus Adolphus knelt upon the ground among his soldiers and thanked the Lord of Hosts for victory, saying, "He holds the field forever." At another time during the Thirty Years' War a Swedish trumpeter captured the ensign of the Imperial army. Pursued by the enemy he found himself trapped with a swollen river before him. He paused for a moment and prayed, "Help me, O my God," and then thrust spurs into his horse and plunged into the midst of the current. The Imperialists were afraid to follow him, whereupon he raised his trumpet to his lips and sounded the defiant notes: "A mighty fortress is our God!" George N. Anderson, a missionary in Tanganyika Province, British East Africa, tells how he once heard an assembly of 2,000 natives sing Luther's great hymn. "I never heard it sung with more spirit; the effect was almost overwhelming," he testifies. A West African missionary, Christaller, relates how he once sang "Ein feste Burg" to his native interpreter. "That man, Luther," said the African, "must have been a powerful man, one can feel it in his hymns." Thomas Carlyle's estimate of "Ein feste Burg" seems to accord with that of the African native. "It jars upon our ears," he says, "yet there is something in it like the sound of Alpine avalanches, or the first murmur of earthquakes, in the very vastness of which dissonance a higher unison is revealed to us."