Service in the Organized Reserve during the interwar period was not as appealing as the Army expected, and suffered because of limited funding that restricted training opportunities.

Turnover in the Officers' Reserve Corps was high, as many men in mandatory ROTC had little interest in military affairs, and allowed their five-year commissions to expire without applying for reappointment.

Enlistment in the ERC was restricted to those men "who have had such military or technical training as may be prescribed by regulations of the Secretary of War."

By the end of 1942, 140,000 officers holding Reserve commissions through various paths were on active duty, but by that date, 12,100 who had been previously commissioned "had not received such orders," mainly for reasons like being over-age in grade, found medically disqualified for active service, deferred due to academics or civilian employment, or lack of vacancies.

On 6 February 1942, President Franklin D. Roosevelt signed Executive Order 9049, which ordered "into the active military service of the United States...for the duration of the present war and for six months after the termination thereof...each of the organizations and units and all of the personnel of the Organized Reserve not already in such service;" because most Reserve officers were already on sctive duty, this amounted to a “public relations” document.

"[9] The order and timetable in which Organized Reserve infantry divisions were ordered to active duty was based upon the number of World War I battle honors earned (if applicable), the location and availability of training sites, and the ability of the Army to furnish divisional cadres and filler replacements.

A tentative troop basis for the Organized Reserve Corps (ORC), prepared in March 1946, outlined 25 divisions: three armored, five airborne, and 17 infantry.

Although the dispute over Class A units lasted several months, the War Department proceeded with the reorganization of the Organized Reserve Corps divisions during the summer of 1946.

That all divisions were to begin as Class C (officers only) units, progressing to the other categories as men and equipment became available, undoubtedly influenced the decision.

Recognizing the importance of the Organized Reserve to the World War II effort, Congress authorized retirement and drill pay for the first time in 1948.

The Section V Committee opposed the reduction of the Organized Reserve Corps from twenty-five to thirteen divisions because it feared unfavorable publicity, particularly with the nation at war.

On 20 December the Vice Chief of Staff of the United States Army, General John E. Hull, directed the reorganization and redesignation of airborne and armored divisions as infantry as soon as practicable.

Before the dust had settled on the reforms, the Army realized that it had failed to improve unit manning or meet reasonable mobilization requirements.

While the Korean War was still underway, Congress began making significant changes in the structure and role of the Army Reserve.

With the elimination of the 79th, 94th, 96th, and 103d Infantry Divisions, the Army decided to retain their headquarters as a way to preserve spaces for general and field grade officers.

Some former divisional units assigned to the four divisions were used to organize four brigades, which added flexibility to the force as well as provided four general officer reserve billets.

In November 1965, a long-standing controversial goal of the Defense Department, a reduction of the reserve troop basis, was achieved.

Those reserve units that were judged unnecessary and others that were undermanned and underequipped were deleted and their assets used to field contingency forces.

[15] In the post-Cold War draw-down, all of the Army Reserve's combat units were disbanded, except the 100th Battalion, 442nd Infantry Regiment.

Many RC Soldiers are organized into Army Reserve Troop Program Units (TPUs), while others serve in active Army units as Individual Mobilization Augmentees (IMAs), or are in non-drilling control groups of the Individual Ready Reserve (IRR).

All United States Army soldiers sign an initial eight-year service contract upon entry into the military.

Occasionally, the contract specifies that some of the service will be in the Regular Army (also called Active Component (AC)) for two, three, or four-year periods; with the remaining obligation served in the RC.

Soldiers entering directly into the U.S. Army Reserve nevertheless encompasses a period of initial entry training (IET).

Soldiers who, after completing the AC portion of their enlistment contract choose not to re-enlist on active duty, are automatically transferred to the RC to complete the remainder of their Statutory Obligation (eight-year service total) and may be served in a drilling Troop Program Unit (TPU), Individual Mobilization Augmentee (IMA), or Individual Ready Reserve (IRR) status.

Non-commissioned officers of the rank of Staff Sergeant (E-6) and above will reenlist for an indefinite status after they have served for 12 years of service or more.

Members of the IRR are encouraged to take advantage of training opportunities and are eligible for promotion provided all requirements are met.

As such, they no longer hold the statutory dual-status defined in the National Guard Act of 1934, as members of both their State’s militia and the federal reserve component.