Upon graduating from boot camp, he served on board the USS Lexington (The Mighty Lex) aircraft carrier at sea.

[3] After the United States entered World War II, Sergeant Severance was sent to Officer Candidates School and commissioned as a second lieutenant.

In 1943, Severance was deployed to the Pacific Theater with the Paramarines, and by November, his unit was taking part in the Bougainville campaign.

At Bougainville, Severance proved himself in battle by leading his cut off platoon out of a Japanese ambush with minimal casualties.

[3][5] In September 1944, Severance and the rest of the 5th Marine Division left San Diego for Camp Tarawa, Hawaii.

[6] In January 1945, the division left Camp Tarawa, stopping for a brief liberty at Pearl Harbor, before sailing west across the Pacific Ocean bound for Iwo Jima.

At approximately 09:55 on February 19, 1945, Severance led Easy Company ashore with the twelfth wave at Green Beach One during the battle of Iwo Jima.

[8] Easy Company landed unopposed and was in the assembly area on the beach for roughly 20 minutes before the defending Japanese finally opened fire on the invasion force.

[10] Severance led Easy Company off the beach under heavy fire and played a role in helping to cut Mount Suribachi off from the rest of the island before the day was over.

[12] On February 23, Lieutenant Colonel Chandler W. Johnson, 2/28's commanding officer, ordered Severance to send one platoon up the face of Suribachi.

Johnson then sent his assistant operations officer, Second Lieutenant Ted Tuttle, down to the beach to secure a larger flag to raise over Suribachi.

Severance ordered four Marines from 2nd Platoon, Sergeant Michael Strank, Corporal Harlon Block, and Private First Classes Ira Hayes and Franklin Sousley to reel a telephone wire up the mountain from the battalion command post.

He then sent his runner, Private First Class Rene Gagnon, to the battalion command post to obtain radio batteries for Schrier.

The first flag was brought back down Suribachi and returned to Lieutenant Colonel Johnson, who promptly placed it in the battalion safe.

[20] Severance continued leading Easy Company in the battle after the flag raising, advancing over the northeast end of the island.