The only Marine Division that, as an entire unit, never spent as much as one day in the continental United States was the Sixth Marine Division. It was composed of three infantry regiments; the 4th Marines, 22nd Marines and 29th Marines, an artillery regiment, the 15th Marines and subordinate units such as Engineer, Medical, Pioneer, Motor Transport, Tank, Headquarters and Service battalions.
The division was created on Guadalcanal in the Solomon Islands in September of 1944. The core about which the division was formed was the First Provisional Marine Brigade, which included the 4th Marines, the 22nd Marines and the artillery battalions that had supported those two Marine regiments and which later were combined and expanded into the 15th Marines. The 1st Provisional Marine Brigade fought as a unit in the invasion and retaking of Guam in the Marianas Islands. The brigade was awarded the Navy Unit Citation for its actions on Guam.
After the fighting on the Island of Guam was ended, the brigade was joined on Guadalcanal by the 1st Battalion of the 29th Marines, which had fought with the Second Marine Division on Saipan in The Marianas. The 2nd and 3rd battalions of the 29th Marines left the United States on August 1, 1944 and joined the rest of the Sixth Marine Division on Guadalcanal.
While the Sixth Marine Division was a new division when it was created, its component units were anything but new. Of its nine infantry battalions, seven of them had fought in at least one island battle, most in at least two battles. The 2nd and 3rd Battalions of the 29th Marines were new units, but with many noncommissioned and commissioned officers who were overseas for the second time, having fought as members of other Marine Divisions.
After training on the Island of Guadalcanal, the division steamed 6000 miles to land on the Island of Okinawa on April 1, 1945. The division then fulfilled its mission of capturing the northern half of that island.
In late April the division moved south to join in the assault of a strong Japanese defense line that had been constructed across the southern part of the Island of Okinawa. That line was located in hills that were honeycombed with caves and passages, sometimes having three or more levels. It was possible to traverse the line from coast to coast and be underground almost all the way. The Marines and soldiers assaulting that line were met by well registered mortar and artillery fire, as well as machine guns with interlocking fields of fire. A high price was paid for each yard gained against that line, with the blood of men killed and wounded being the currency.
The Battle of Okinawa was a long one, lasting 82 days. The Sixth Marine Division had nearly 1700 Marines and Navy Medical Corpsmen who were killed in action or died of wounds, with more than 7400 being wounded in action. It has been said that when a military unit suffers ten percent casualties it loses its effectiveness. Such was not the case in the Sixth Marine Division. The highest casualty rates were in the rifle companies, many of which were reduced to the level of under strength platoons, with non commissioned officers commanding them. While being nowhere near as effective as when at full strength, these under strength units were still coherent Marine Companies and still fighting.
Any Marine believes that his unit is the best, and this is as it should be. But the Sixth Marine Division was at least the equal of any Marine division that fought in the Pacific Theater in World War Two. The Division was decorated with the Presidential Unit Citation for it heroism on the Island of Okinawa. Requirements for the award of that decoration are that the unit as a whole performed in a manner that would have merited the Navy Cross Medal to an individual Marine.
After the Japanese surrender, the Sixth Marine Division, less the 4th Marines, sailed to Tsingtao, China to accept the surrender of the Japanese there. The 4th Marines went to Japan. The division occupied Tsingtao until April 1, 1946. On that date, the division, downsized by the loss of many of its Marines who had returned to the United States, was designated as the 1st Provisional Marine Brigade. One year to the day after its landing on the Island of Okinawa, the Sixth Marine Division had ceased to be.