With the success of the British offensive at Amiens, Gen John “Blackjack” Pershing requested an American-led offensive against the salient at St Mihiel. The reduction of the salient would prevent the Germans from shelling the newly liberated Amiens rail line and significantly ease Allied logistical problems. Foch approved, but as the unexpected success of the Amiens offensive began to unfold, told Pershing to plan for a general offensive by the end of September, and scrap the St Mihiel. The general offensive from the Meuse-Argonne would make the St Mihiel salient untenable and an offensive unnecessary. Pershing disagreed, mostly because the St Mihiel salient spilt the American forces. As they stood, only the southern American troops would be under American army command for the general offensive; the northern troops would fall under French command. If the St Mihiel salient was reduced Pershing could feasibly construct an American army group of two American armies, commanded by himself, which would put him on par with Haig and Foch. He enlisted the help of France’s greatest American advocate, Marshal Petain to make it happen. Petain and Pershing argued that if the troops in the St Mihiel salient were captured, they would be unavailable to defend against the general offensive two weeks later. Furthermore they assured Foch that the St Mihiel offensive would not affect or delay the general offensive from the Meuse-Argonne two weeks later. Foch relented, and approved the first American led army level offensive of the Great War.
On 10 September 1918, two American corps attacked the flanks of the salient while a French corps under American command attacked the apex. Pershing was not going to let this attack fail and secured an overwhelming amount of support in terms of tanks, artillery and planes. Despite the fact that the St Mihiel salient was not overrun since the Germans captured it in 1915 and the Germans built it into a fortress, the Americans made good progress. The Germans put up stubborn resistance but more out of habit than anything else. They had been ordered to withdraw to shorten the line on the 8th of September, but took their time. On 12 September, America’s premier division, the 1st US Infantry Division, drove from the south and linked up with the 26th “Yankee” US Infantry Division (of Sgt Stubby fame), which closed the pocket.
At a cost of 7,000 casualties, Pershing inflicted 17,000, mostly captured, and secured his flanks for the upcoming general offensive. The Allied logistics were eased considerably by the shortening of the line and the push east. Most importantly, Pershing, his commanders, and his staff gained invaluable experience for the larger and more complex general offensive that was to occur at the end of the month.