In 1860 came the Seven Weeks' War with Austria. Prince Frederick Charles was appointed to command the I. Army, which he led through the mountains into Bohemia, driving before him the Austrians and Saxons to the upper Elbe, where on the 3rd of July took place the decisive battle of Koeniggraetz or Sadowa. This was brought on by the initiative of the leader of the I. Army, which had to bear the brunt of the fighting until the advance of the II. Army turned the Austrian flank. After the peace he returned to the III. army corps, which he finally left, in July 1870, when appointed to command the II. German Army in the war with France. In the early days of the advance the prince's ruthless energy led to much friction between the I. and II. Armies (see FRANCO-GERMAN WAR), while his strategical mistakes seriously embarrassed the great headquarters staff. The advance of the II. Army beyond the Saar to the Moselle and from that river to the Meuse displayed more energy than careful strategy, but herein at least the "Red Prince" (as he was called from the colour of his favourite hussar uniform) was in thorough sympathy with the king's headquarters on the one hand and the feelings of the troops on the other. Then came the discovery that the French were not in front, but to the right rear of the II. Army (August 16). Alvensleben with the III. corps held the French to their ground at Vionville while the prince hurried together his scattered forces. He himself directed with superb tactical skill the last efforts of the Germans at Vionville, and the victory of St Privat on the 18th was due to his leadership (see METZ), which shone all the more by contrast with the failures of the I. Army at Gravelotte. The prince was left in command of the forces which blockaded Bazaine in Metz, and received the surrender of that place and of the last remaining field army of the enemy. He was promoted at once to the rank of general field marshal, and shortly afterwards the II. Army was despatched to aid in crushing the newly organized army of the French republic on the Loire. Here again he retrieved strategical errors by energy and tactical skill, and his work was in the end crowned by the victory of Le Mans on the 12th of January 1871. Of all the subordinate leaders on the German side none enjoyed a greater and a better deserved reputation than the Red Prince.