Thread by @pptsapper

At 0100 this morning 100 years ago, thousands of US guns opened fire in a deafening crescendo of steel. In the 26th Division sector alone were 202 guns of all calibers, from trench mortars all the way up to massive railway guns. The St Mihiel Offensive had begun.

Across the lines, the guns paused for a five minute sound ranging an hour before the infantry advance. Germans who scrambled out of their dugouts to man defensive positions were caught in a hail of steel and high explosive when the bombardment resumed.

On the south end of the Salient, the @FightingFirst, 42nd, 89th, 2nd, 5th, 90th, and @82ndABNDiv (still legs) went over the top at 0500, attacking from south to northwest. US Renault FT17 tanks rolled forward over the wet ground in support of the infantry.

The allied forces on the west side of the Salient held in place until 0800, allowing the Germans to commit reserves to the southern end. But at 0800 the preparatory gunfire shifted to a creeping barrage & the 26th and 4th Divisions went over the top with 4 French divisions.

Facing this onslaught were around 55,000 German troops left in the Salient. They were to have been withdrawn over the next two days, as many of the heavy guns had been, but the US attack precipitated the withdrawal order. Now they held on as best they could to buy time.

On each side of the Salient, allied & US troops steadily pushed forward. Opposition stiffened by mid-morning, but MG nests & pillboxes were methodically neutralized by artillery, MGs, tanks, or flanking squads. This was no 2nd Marne bloodbath. This was combined arms warfare

The forces on the southern edge of the Salient make 5 miles on the first day. Those on the western edge gain 2 miles. They seize thousands of prisoners. Many come out of dugouts to surrender to the second wave after the first wave passes over them. Roads become clogged w traffic

Engineers swarm over the cratered roads to allow US and allied reserves and supply trains to reach the ever-moving front lines as streams of wounded & prisoners move in the other direction. Rains over the previous days have left the sector a sodden mess.

Some of Patton's tanks bog down in the wet ground, but most power forward to support the assault along the southern edge. There are hiccups as tanks & infantry learn how to fight together. Learn more about this in our @WarStoriesCast episode on the topic.
iheart.com/podcast/263-wa…

By nightfall, all the US day one objectives had been reached. But the pocket had not been closed. So Pershing sent messages to the commanders of the 1st and 26th Divisions: link up in Vigneulles by morning to close the pocket and prevent the escape of the remaining Germans.

One of Pershing's staff officers messaged MG Edwards, 26th Division commander: "Vigneulles is yours to lose." Edwards, never a man to back down from a challenge from Pershing, grabbed the 102d INF & sent them on an all-night march down the Tranchee de Calonne to Vigneulles

By morning, the US lines are moving forward again, aiming at straightening the line. US horse cavalry makes its only action of the war south of Vigneulles, knocking some German helmets in. Lead scouts from @CTARNG's102nd INF are within sight of Vigneulles, Montsec in the distance

By noon, the 102nd has taken Vigneulles in a sharp fight & spots what appears to be hostile infantry from the south. Scouts carefully fan out. As the infantry gets closer, they realize they're doughboys; the @FightingFirst has arrived & the linkup is complete.
#fww #WW1

By September 16, the St. Mihiel Salient was no more. At the time, it had been America's largest battle, with 550K troops taking part. That title would not last, as in 10 days the AEF would begin America's largest & bloodiest battle ever: the Meuse-Argonne Offensive.
#WW1

If you've enjoyed this, make sure you're following @Erikhistorian @MichaelNeiberg @WW1CC @100ansHM @Aisne1418 @USArmyCMH for more information on the US in #WW1

Suggested reading:
Last of the Doughboys
The AEF Way of War
Make the Kaiser Dance
The Hello Girls
Back Over There