In September 1939, the world again was thrust into a global conflict after Germany unexpectedly attacked Poland, officially starting World War II.

The U.S. began to supply aid to the Allied Forces of Great Britain and France against the Axis Powers in Europe of Germany and Italy. At the same time, the U.S. was carefully watching its territories in the Pacific as the Japanese began advancing across the ocean.

On the morning of Dec. 7, 1941 at Pearl Harbor, Hawaii, the idea of the U.S. remaining neutral in the war ended after the Japanese launched an attack against U.S. soil, a day that President Franklin D. Roosevelt referred to as, "a date which will live in infamy."

Being forced to assemble an Army to fight in both Europe and the Pacific, the Army began a massive recruitment of new Soldiers.

The Army began using non-commissioned officers who were on active duty prior to the war as the primary trainers for troops destined for overseas duty.

NCOs also, for the first time, found themselves able to apply for transfers to new branches, as the creation of the Paratroopers and Paragliders offered new career opportunities. These new branches offered more pay and new challenges for NCOs looking to advance their career.

These new branches, along with the massive mobilization, would increase the number of NCOs at a faster rate than ever in history. In 1941, the amount of NCOs in the enlisted ranks was 20 percent; that number would grow to 50 percent by then end of the war in 1945.

With the vast amount of casualties suffered in the war, enlisted men rose through the ranks very quickly during World War II. This resulted in a perceived lessening of the prestige of the NCO to some higher enlisted NCOs who obtained their rank prior to the war. Soldiers were quickly promoted from private to corporal; and corporal to sergeant after only serving a small amount of time in the unit.

The NCO also saw changes in the field, where in the infantry, the corporal was officially replaced as the squad leader by sergeants, and the infantry squad also grew from eight men to 12.

For the first time ever, due to a shortage in manpower, the Army formally added women into its ranks. Women served in supply, communications, electrical, mechanical and other support careers during the war.

Though it was a slow transition with only 11,000 women in the Army in 1941, by the end of the war 93,000 women wore a uniform. When the war ended, 37 percent of the women in the Army had achieved the rank of corporal or above.

In the Pacific, as the Japanese quickly advanced, troops found themselves cut off from being resupplied. NCOs were forced to prepare their units for Japanese attacks, while at the same time find enough food to feed their troops. Many units began hunting their own meals in the form of water buffalo, horses, monkeys and other animals found on the islands.

In Europe, NCOs would lead troops across Africa, Italy, France, Netherlands and Germany on their way to V-E Day.

During this time NCOs would lead Soldiers in two of the largest operations in the history of warfare. The first being the amphibious assault of Normandy, France, during Operation Overlord and the second being the airborne attacks in the Netherlands during Operation Market Garden.

The war in Europe officially ended in May 1945 with Germany's surrender, three months later, in August, Japan officially surrendered after the U.S. dropped atomic bombs on the cities of Nagasaki and Hiroshima.

That same year, in 1945, Congress passed a legislation that allowed enlisted men with at least 20 years, but no more than 29, to be placed on a retirement list. The Soldier would remain in the reserve until completing 30 years of service, collecting two and a half percent of their average pay for the six months preceding the retirement.

After the war, the technical ratings first implemented in 1930s were officially dropped, placing more emphasis on Army wide standards for NCO selection and training.

The NCO Corps began to make more changes to their professional development program with the Career Guidance Plan and NCO Schools, though in the midst of change, the NCO Corps found itself fighting communist breakout with the start of the Korean and Vietnam Wars.