The first French army, after a violent struggle, conquered the passes of the Vosges, but the conquest was vigorously opposed and took more time than the French had reckoned on.  As soon as it had become master of the Donon and the passes, the first French army pushed forward into the defile of Saarburg.  At St. Blaise it won the first German colors, took Blamont and Cirey (August 15, 1914), seized the defiles north of the canal of the Marne and the Rhine, and reached Saarburg.  Here a connection was established with the army of Lorraine, which had commenced its operations on the 14th.  A violent battle ensued, known under the name of the Battle of Saarburg.  The left wing of the French army attacked August 19, 1914; it hurled itself at the fortified positions, which were copiously fringed with heavy artillery.  In spite of the opposition it made progress to the northwest of Saarburg.

On the 20th the attack was renewed, but from the beginning it was evident that it could not succeed and that the duty intrusted to the Eighth Army Corps of opening up the way for the cavalry corps could not be accomplished.  This army corps had gone through a trying ordeal as a result of the bombardment by the heavy German artillery established in fortified positions, covering distances all measured in advance, with every group and French battery presenting a sure target and the action of the French cannon rendered useless.

If the left wing of the First Army found itself checked, the center and the right on the other hand were in an excellent position and were able to advance.  But at this point (August 21, 1914) the Second French Army (the army of Lorraine) met a serious reverse in the region of Morhange and was compelled to retreat.  This retreat left the flank of the First Army gravely unprotected, and as a consequence this army was also obliged to fall back.  This rear-guard movement was accomplished over a very difficult piece of country down to the Baccarat-Ban de Sapt-Provenchere line, south of the Col du Bonhomme.  It was found necessary to abandon the Donon and the Col de Sapt.

The task committed to the Second Army, that of Lorraine under De Castlenau, was to protect Nancy, then to transfer itself to the east, advancing later to the north and attacking in a line parallel to that taken by the First Army on the Dieuze-Chateau Salins front in the general direction of Saarbruecken.  Its mission was therefore at once both offensive and defensive:  to cover Nancy and continue toward the west the attack of the First Army.

After having repulsed, August 10 and 11, 1914, the strong German attacks in the region of Spincourt and of Chateau Salins the Second Army took the offensive and went forward almost without stopping during four days of uninterrupted fighting.  Penetrating into Lorraine, which had been annexed, it reached the right bank of the Selle, cut off Marsal and Chateau Salins, and pushed forward in the direction of Morhange.  The enemy fell back; at Marsal he even left behind enormous quantities of ammunition.