Major General William H. Rupertus wrote it during World War II following the attack on Pearl Harbor between late 1941 and early 1942, but its first publication was in San Diego in the Marine Corps Chevron on March 14, 1942.
His reasoning for writing the Creed is believed to be that he felt that his men had to understand the concept "that the only weapon which stands between them and Death is the rifle...they must understand that their rifle is their life..."[1] In the past, all enlisted Marines would learn the Creed at recruit training.
[2] The Rifleman's Creed continues to stand as a pillar concerning the ethos of the Marine Corps.
The Rifleman's Creed is one of the keystones of the United States Marine Corps doctrine and helps designate that every Marine is, first and foremost, a Rifleman regardless of Military Occupational Specialty (or MOS) designation.
[1] Even now, in the United States Marine Corps rifle training data book, given to recruits when undertaking Table 1 of rifle qualification, the Rifleman's Creed is printed within the data book to ensure that prior to picking up a weapon a Marine understands what their rifle means to them and their Corps.
"[3] The Creed itself utilizes a sense of anthropomorphism in order to coerce Marines into seeing their rifle as more than a simple tool of war.
I will ... My rifle and I know that what counts in war is not the rounds we fire, the noise of our burst, nor the smoke we make.