How did jimmy cross become a first lieutenant in The Things They Carried?

In "The Things They Carried," Jimmy Cross becomes a first lieutenant primarily due to his leadership qualities and the responsibilities he undertakes for his men during the Vietnam War. His promotion reflects his dedication to the soldiers under his command, as he grApples with the emotional burden of leadership, especially after the death of Ted Lavender, which deeply impacts him. Cross is portrayed as a character torn between his duties and his feelings for Martha, highlighting the complexities of war and personal sacrifice.