You can check out this article on Harry Truman’s service in the artillery in World War I. Battery D, his unit, wasn’t the easiest:
On 11 July Truman replaced Captain John Thatcher as commander of Battery D. The men of Battery D were unhappy with the change, as Thatcher had been very popular. Truman's letters to Bess indicated that he was extremely happy with this assignment, that being a battery commander was his main ambition. Battery D had a bad reputation, was known as Dizzy D, and had gone through four battery commanders in eleven months. The 194-man battery was mostly (96 percent) Irish and German Catholics, many of whom were college students from Rockhurst College in Kansas City, fond of breaking army regulations. On the day that Truman took over Battery D, the men of the battery gave him the Bronx cheer when they were dismissed from formation. Some staged a fake stampede of the horses and got into a fight that sent four men to the infirmary. Truman called all the non-corns together, told them that they were responsible for their own sections and that "I didnt come here to get along with you. Youve got to get along with me...." Things improved after that.