At the outbreak of the war, Bonnyman was exempt from any military obligation due to his role in running a company producing strategically vital material for the war effort.
Nevertheless, he enlisted in the U.S. Marine Corps as a private at Phoenix, Arizona.
Bonnyman received his recruit training at Marine Corps Recruit Depot San Diego, California.

In October 1942, Bonnyman sailed for the South Pacific aboard the SS Matsonia.
He distinguished himself at the Battle of Guadalcanal as part of a Marine pioneer unit (akin to a lightly equipped version of an Army combat engineer group).
In February 1943, he received a battlefield commission to the rank of second lieutenant in recognition of what his superiors described as exceptional leadership skills.

Bonnyman's civilian background, temperament and skills would come to play an important role at Tarawa in November 1943, where he was assigned to a shore party handling beachhead logistics.
When the assault troops were pinned down by heavy enemy artillery fire at the seaward end of the long Betio Pier, on his own initiative Bonnyman organized and led five men over the open pier to the beach.
There he voluntarily obtained flame throwers and demolitions and directed the blowing up of several hostile installations.

On the second day of the struggle, Bonnyman, determined to breach the enemy's strong defensive line, led a demolition team of 21 Marines in an assault on the entrance to a huge bombproof shelter which contained approximately 150 Japanese soldiers.
The enemy position was about forty yards forward of the Marine lines.
 Bonnyman advanced his team to the mouth of the position and killed many of the defenders.
 His team was forced to withdraw to replenish its supply of ammunition and grenades.
Bonnyman again pressed his attack and gained the top of the structure, thereby flushing more than one hundred of its occupants into the open where they were cut down by Marine infantry and a supporting tank.
When the Japanese returned fire, Bonnyman stood on the forward edge of the position and killed three of the attackers, but was himself killed as he ordered more charges brought forward.
The battle continued for another 10–15 minutes, with all of the Japanese defenders flushed out.
Of Bonnyman's original assault party of 21 Marines, 13 had survived.
Betio Island was declared secured on the same day.
At the outbreak of the war, Bonnyman was exempt from any military obligation due to his role in running a company producing strategically vital material for the war effort. Nevertheless, he enlisted in the U.S. Marine Corps as a private at Phoenix, Arizona. Bonnyman received his recruit training at Marine Corps Recruit Depot San Diego, California.
In October 1942, Bonnyman sailed for the South Pacific aboard the SS Matsonia. He distinguished himself at the Battle of Guadalcanal as part of a Marine pioneer unit (akin to a lightly equipped version of an Army combat engineer group). In February 1943, he received a battlefield commission to the rank of second lieutenant in recognition of what his superiors described as exceptional leadership skills.
Bonnyman's civilian background, temperament and skills would come to play an important role at Tarawa in November 1943, where he was assigned to a shore party handling beachhead logistics. When the assault troops were pinned down by heavy enemy artillery fire at the seaward end of the long Betio Pier, on his own initiative Bonnyman organized and led five men over the open pier to the beach. There he voluntarily obtained flame throwers and demolitions and directed the blowing up of several hostile installations.
On the second day of the struggle, Bonnyman, determined to breach the enemy's strong defensive line, led a demolition team of 21 Marines in an assault on the entrance to a huge bombproof shelter which contained approximately 150 Japanese soldiers. The enemy position was about forty yards forward of the Marine lines.  Bonnyman advanced his team to the mouth of the position and killed many of the defenders.  His team was forced to withdraw to replenish its supply of ammunition and grenades. Bonnyman again pressed his attack and gained the top of the structure, thereby flushing more than one hundred of its occupants into the open where they were cut down by Marine infantry and a supporting tank. When the Japanese returned fire, Bonnyman stood on the forward edge of the position and killed three of the attackers, but was himself killed as he ordered more charges brought forward. The battle continued for another 10–15 minutes, with all of the Japanese defenders flushed out. Of Bonnyman's original assault party of 21 Marines, 13 had survived. Betio Island was declared secured on the same day.
Alexander Bonnyman Jr.