At exactly 1:18 P.M. on April 6, 1917, the United States declared war on Germany, committing American forces to the First World War. As a member of the Missouri National Guard, Truman was inspired by Wilson's call to arms and left the farm in the hands of his sister. He headed off to prepare for war and was elected a First Lieutenant in Battery F. The federal call to the Missouri National Guard came on August 5^th. The regiment became known as the 129^th Field Artillery of the 60^th Brigade attached to the 35^th Division.

The first stop for Truman's regiment was Camp Doniphan near Fort Sill, Oklahoma. Not long after his arrival on September 26^th, Truman was made regimental canteen officer. With no experience in merchandizing, Truman quickly recruited Sergeant Edward Jacobson to assist him. Then they instigated several plans. The canteen needed capital to get started. He got each company to provide approximately $2 per man. This amounted to about $2200. Then each company provided one man a day to work at the canteen after drilling practices. For the day's work, each man received a dollar from canteen profits. Then Harry got the company barbers assigned to the canteen and they were paid 40% of whatever they brought in. Truman and Jacobson were so successful that in six months, they had returned $10,000 in dividends to the contributing mess funds.

Truman was interviewed for promotion just prior to his regiment leaving Fort Doniphan on March 20, 1918. They sailed for Europe from New York on a confiscated German luxury liner renamed the George Washington on the evening of the 29^th. His promotion to the rank of captain followed on April 23^rd.

The American Expeditionary Forces (AEF) at that time numbered nearly a million men in France. The George Washington arrived with its seven thousand men in Brest, France on April 13, 1918. By the war's end, the AEF would number two million.

The first few months in France were easy going for Truman. Officers stayed in fine hotels. Truman's room had double lace curtains and a white marble mantelpiece. The chairs were upholstered in red plush. Most of the men spent their time with the ladies who were very much interested in the American men. Truman would have nothing to do with the womanizing, as his true love waited patiently back home.

First Lieutenant Edgar Hinde would later recall, "Personally, I think Harry is one of the cleanest fellows... the cleanest fellows morally that I ever saw, or know. I never saw him do anything out of the way that would be questionable in the way of a moral situation. He was clean all the way through. I always admired him for that quality and you know when a man's in the Army, why his morals get a pretty good test."¹

Truman was sent to artillery school in the town of Chaumont. After his training he was made Battery Commander of Battery D in charge of 4 guns and 194 men and sent to the front. Battery D was largely comprised of Irish Catholics from Kansas City. Truman discovered that he was assigned these men after they had been through several other commanders who couldn't tame this wild bunch of Irishmen.

When Harry stepped in front of these men for the first time he was scared to death. He just stood in front of them for a while until he finally got command of his own voice, and simply said, "Dismissed!" To this he was greeted with the Bronx cheer.

The men played all sorts of pranks throughout the day and got into fights. The next morning, Truman posted a list of all the noncommissioned officers who had been busted in rank. Then he called a meeting of the rest of the things out, or get along with him, to let him know right then and he would bust them as well. In just a few words, he reminded them that he hadn't been set there to get along with them, that they had to get along with him. After that, he had no more problems with the men. In fact, they became one of the best regiments in the 12th Field Artillery.

The first action for Battery D came on the evening of August 29 at 8:00 P.M. when they were ordered to open fire on German batteries some four miles away. They fired 500 rounds of poison gas at the enemy positions. The idea was to move from the position as quickly as possible after firing, before the Germans could return fire. Unfortunately the sergeant responsible for bringing up the horses was nowhere to be found, and got the horses up a half an hour later. The men were scrambling to get out of the position when a German shell exploded only 15 feet from Truman who was on horseback. The shell hit the horse and it fell over, pinning Harry underneath. By the time they pulled him out, he was gasping for breath. To make matters worse, the men in their panic, had pulled the guns in the wrong direction and got them bogged down in the mud. The panic didn't end there as the sergeant, who had brought the horses up late, began screaming that the Germans knew their position. He began running, causing a general panic, with many of the men also running. Truman stood his ground, letting loose with a long, loud barrage of profanity, shocking the men into recovery. With two horses dead, and two others which had to be destroyed, it was impossible to get the guns from the mud. Truman ordered his men back to base camp. They would have to retrieve the guns later when they had more horses. With what he considered a dismal failure, Truman feared for his job. Truman's commanding officer told him that many green troops behaved that way initially. He recommended that the guilty sergeant be court-martialed. Truman couldn't bring himself to have the man court-martialed, instead he busted him to private and transferred him to another unit.

Truman won the respect of his men for how he stood up under fire. When it came time for the dangerous mission to rescue the guns, every man volunteered. Truman only took the men and horses necessary to complete the task, unwilling to put them all in danger. Truman would describe his first combat experience in a letter to Bess Wallace, written on September 1, 1918 in this way: "My greatest satisfaction is that my legs didn't succeed in carrying me away, although they were very anxious to do it."

On September 16 the orders for the final great offensive were given--nothing the likes of which had ever been seen before. The great Meuse-Argonne offensive was under way and Truman's Battery D would begin a 100-mile forced march. Their destination was Hill 290, near the village of Neuvilly. Truman's men arrived at their designated location at 3:00 A.M. It took all they had to get the four guns into position in the mud and pouring rain before daylight. Three days would be spent clearing trees for a line of sight and making preparations for the assault. It was here that Truman came close to losing his life. On the second night, German shells exploded on the spot where Truman had slept the morning they had arrived. Had he not changed positions, there is no way he would have survived the shelling.

On September 26th at 4:20 in the morning, the battery was given orders to fire 1,000 rounds per hour. With four guns, this meant each gun would be firing six rounds per minute, allowing 10 minutes an hour for the guns to cool down. The infantry would move out at 5:30 A.M. and the artillery would fire over their heads, advancing 100 meters every four minutes. If any of the gunners made a mistake it could mean the life of some of the allies.

The 129^th Field Artillery was ordered forward in support of the infantry. The following day they again moved forward. In the evening, Truman and several of his men went forward to establish a spotting position, looking for enemy artillery. While they were there, an American plane dropped a flare over a location where the enemy was beginning to set up artillery. Truman waited for the enemy to set the guns in place, and then pull back all of their horses so that the guns couldn't be moved quickly. He then called back the coordinates to his men who opened fire on the German guns. Truman violated an order by firing on the German position, because the German artillery unit was not in the sector Truman was assigned to protect. Had Truman not made this decision, the 28^th Division would have had to face those guns in the morning and would have experienced much higher casualties. Colonel Klum, Truman's commander, threatened him with a court-martial but nothing came of it.

On November 11, 1918 with Battery D fully engaged at 8:30 A.M, Truman was given the order that at 11:00 A.M the Germans would sign the armistice. The armistice would be signed on the eleventh hour of the eleventh day of the eleventh month. Truman was ordered to continue firing at his assigned intervals. Truman said that Battery D's last shell was fired at 10:45 A.M. on November 11, 1918.

After the armistice it would take time to move all the men and equipment home. Truman got a chance to visit Paris where he saw Woodrow Wilson ride by in a car. It was there also that he bought a wedding ring for his future bride. On April 9, 1919, the 129th Field Artillery set sail for home on the German luxury liner Zeppelin.