From the Lorraine Gap to the St. Mihiel Salient

View of Woevre Plain from Montsec;
Meuse Heights in Distance;
Occupied by German Army, Sep 1914–Sep 1918

In the fall of 1914, a 40-mile gap, nearly void of attackers or defenders, opened in eastern France for a short period of time that no one seemed to have anticipated. In the following scramble the gap would be closed, but the stabilized section of the front would create a lasting threat for both sides. American sources call it the St. Mihiel Sector and most other parties refer to it as the Woëvre Plain. For the Allies, the final line formed a threatening salient into their defenses; for Germany, it was a back door to the Rhine and the heart of the Fatherland, requiring close monitoring and the strongest possible defenses. 

During the August 1914 fighting around Nancy—discussed in yesterday's article on Roads to the Great War—a different dynamic was unfolding in northern Lorraine. In the opening weeks of the war, a second German army had been heading in the direction of Lorraine—the Fifth commanded by Crown Prince Wilhelm, which was focusing on capturing Verdun. Through August, he had been stymied by the forts around the city, so his staff devised a flanking movement to capture the city by crossing the Meuse to the south and attacking it from the rear. The French, however, had long planned to defend the Meuse and had built a series of forts on the east side of the river, positioned to bombard any troops attempting to cross it. One of these forts would play important roles in the ensuing events: Fort de Troyon north of St. Mihiel directly in the path of the Crown Prince's flanking movement, commanded the river just north of St. Mihiel and would play a critical role in halting the enemy, arguably saving France from a decisive defeat.

French Defenders of Fort Troyon

On 8 September, as the titanic Battle of the Marne was being waged to the west, Fifth Army's 5th Corps arrived on the Meuse Heights with the mission of punching across the Meuse. All that opposed them was a cavalry division on the other side of the river and the 450 defenders and four 120mm and 12 90mm artillery pieces at Fort de Troyon below them. For five days and nights their guns hammered away at the fort, with only occasional intervals. At one point a large German shell set off 60 90mm shells in a magazine. But the French held, with the fort's gunners, engineers, and infantrymen repulsing five separate assaults. Fifth Army could not force the crossing and was bringing up reinforcements and more artillery to force the crossing when a decision was reached on the Marne. Joffre's plan had worked. The prince was ordered to withdraw to the north of Verdun and into the Argonne Forest, in rough alignment with the other German armies deployed north of Reims and along the Aisne River farther west.

Consider the big picture as the bulk of the German forces are withdrawing north, with the bulk of the Allied forces in pursuit. (See map in right column). They are all to the north of Verdun. In the south, the remaining forces have dug in between Nancy and the Swiss border. Between Verdun and Nancy, there is. . .nothing. The existence of this 40-mile "Lorraine Gap," though, will be fleeting.

Situation on 9 September 1914

A strategic opportunity, thus, was opening up between Nancy and Verdun, involving this piece of real estate no one seemed to want for the first six weeks of the war. This Lorraine Gap had some interesting features. Of roughly rectangular shape, it was initially defined by four towns: Verdun and Metz in the north, St. Mihiel and Pont-à-Mousson in the south. Its western boundary is defined by the Meuse River connecting Verdun and St. Mihiel, the eastern boundary by the Moselle flowing between Pont-à-Mousson and Metz. Both rivers have heights (low ridges) on their eastern sides, but the major feature of the region (about three quarters of 150 square miles) is the mostly flat, but in places undulating, flood-prone Woëvre Plain, lying between the Meuse Heights and Metz to the northeast.

Prewar, although three of the four towns, the heights, and most of the plain itself were in French territory, France's planners left the Woëvre undefended, considering the plain impassible. They were satisfied that the line of fortresses along the Meuse Heights and south of the plain provided adequate insurance against a surprise sortie out of Metz to force the Meuse. Indeed, one of these forts, Fort de Troyon, had prevented just such a crossing by the Fifth Army near the end of the Battle of the Marne.

Concrete Trenches Installed After Filling the Gap and Creating the St. Mihiel Salient

Germany would seize the opportunity. On 19-20 September, the remaining detachments from Rupprecht's Sixth Army that had not yet been ordered west for the Race to the Sea sallied forth from Metz over the Woëvre Plain. The French covering forces were rolled back and in nine days of ferocious fighting the German Army had compensated somewhat for their strategic defeat in the Battle of the Marne. Much of the plain and the most defensible positions on the Meuse Heights between Verdun and St. Mihiel had been captured and quickly strengthened. Only late reinforcements out of Nancy prevented the German forces from going even farther, getting into the French rear and really causing havoc. While it was brilliant to seize this opportunity, the assault on the Woëvre was made on a shoestring. Had the German high command retained sufficient forces available to force a crossing of the Meuse River, say, the bulk of the Sixth Army, the course of the war would have changed, maybe decisively. In any case, the shape of the front had quickly morphed from an undefended rectangle to a German salient that threatened Verdun and the rail network of eastern France.

Rupprecht's single action during the post-Marne second war of movement influenced the course of the long war to follow, substantially lengthening the butcher's bill for both sides. The Kaiser's troops had seized a substantial enough portion of the Meuse Heights, the town of St. Mihiel and its adjacent fort, Camp du Romans, to eliminate any traffic, river, rail, or road, into Verdun from the south, and their forces had dug in on the south edge of what came to be known as the St. Mihiel Salient, to make their position impregnable—at least for the next four years, until the Americans arrived.