Why do we call it ARNG 4.0?
In the history of the All Volunteer Force, the ARNG has experienced four phases of development towards becoming an operational reserve:

ARNG 1.0 (1973-1983) — The ARNG saw the need to increase professionalism within its ranks following the end of the Vietnam War. The introduction of the all-volunteer force necessitated a new role for the ARNG. The Total Force Policy, or "Abrams Doctrine," increased reliance on the ARNG, but only as part of the Nation's strategic reserve.

ARNG 2.0 (1984-1991) — The Reagan—era military increased emphasis on training and professionalism across the Army. Though standards for training spread across the Total Army, units fell into a system of tiered readiness and older equipment from the Active Component was used to equip the ARNG. A number of initiatives were introduced during this era to maintain a higher level of readiness. "Round out" maneuver brigades were assigned to Active Component units, and the 1993 Offsite Agreement restructured capabilities between the ARNG and the Army Reserve. By the end of the 1990s, the ARNG was taking on an increasing number of international assistance and peace-keeping missions in Bosnia and Kosovo—a precursor to larger deployments in the future.

ARNG 3.0 (2001-2017) — The terrorist attacks of September 11, 2001 forever changed the ARNG. As the ARNG increased the homeland defense mission, it also began the largest mobilization of ARNG Soldiers since WWII. For 16 years, the Army National Guard became an operational reserve, fighting wars in Iraq and Afghanistan while simultaneously providing forces for rotational deterrence and peacekeeping missions. During this era, the ARNG prepared for rotational deployments with long lead times. With the benefit of modern equipment, lengthy post-mobilization training periods and combat-proven leadership, it quickly became the best-manned, trained and equipped force in the history of the National Guard.

ARNG 4.0 (2017- ) — Today, the ARNG is in the midst of another evolutionary shift. The ARNG maintains its identity as the operational reserve of the all-volunteer Army, one that is trained and equipped better than in the past. ARNG 4.0 builds on the organization's heritage as America's first responder by preparing our Soldiers to train, fight, win, and return home safely with little or no notice. With the smallest Active Component Army since WWII, the ARNG must be poised to excel at any mission the Nation requires of us.

Why do we need to build readiness?
History shows us the tragic consequences of neglecting combat readiness. The history of America's Army includes momentous defeats during the first engagements of major wars. The First Battle of Bull Run in the Civil War, the Battle of Kasserine Pass in the early years of World War I l and the fate of Task Force Smith in the Korean War all serve as examples. America's Army fought and lost these battles because units were unprepared for combat operations against a peer adversary.