For two decades, one Army National Guard brigade has provided the nation with full-time protection against the most powerful weapons on Earth—nuclear-armed intercontinental ballistic missiles.

The 100th Missile Defense Brigade (Ground-based Midcourse Defense), comprising largely Colorado, Alaska and California citizen-soldiers, along with a handful of active component air defenders, is only the size of a Regular Army battalion. It includes one missile defense battalion and administrative control of a space battalion. The brigade has maintained a nonstop wartime-like posture, ready to engage intercontinental ballistic missiles (ICBMs) targeting the U.S. homeland with ground-based interceptors since its alert status began in the fall of 2004.

At its inception, the brigade consisted of a headquarters in Colorado Springs, Colorado; Missile Defense Element crews at Schriever Air Force Base, Colorado, now known as Schriever Space Force Base; the 49th Missile Defense Battalion with its ground-based interceptor security company at Fort Greely, Alaska; and soldiers manning and monitoring Ground-based Midcourse Defense elements at Vandenberg Air Force Base, California, now known as Vandenberg Space Force Base, on a rotational temporary duty basis.

Nod to Past Warriors

Although the brigade has grown to more than 500 soldiers, it has carried the moniker “The 300” since its earliest days, owing to the brigade’s diminutive size when it stood up in October 2003 and in homage to the small cadre of Spartans led by King Leonidas at the Battle of Thermopylae in 480 B.C.

Although the Spartans may have attained most of the historic glory at Thermopylae, they were backed by some 7,000 troops from other Greek city-states and arrayed to stop the invading force at a key location, the chokepoint at the pass of Thermopylae. The 100th Missile Defense Brigade soldiers manning the “tip of the shield” are just the more visible element of a larger force comprising space, land and sea-based missile warning and defense architecture with joint units around the world.

ICBMs also have a chokepoint, during the exoatmospheric “midcourse” phase of their flight. This is where the Ground-based Midcourse Defense System’s ground-based interceptors, launched by 100th Missile Defense Brigade soldiers, clash with nuclear reentry vehicles.

New Mission

The 100th Missile Defense Brigade was activated by presidential directive during the height of the global war on terror. Although Ground-based Midcourse Defense was a new mission, National Guard units serving strategic national defense missions was not new. Guard units proved more than capable at the height of the Cold War and during the Vietnam War, manning and operating some of the nation’s Nike air defense systems across the United States.

Modern Ground-based Midcourse Defense soldiers have distinct differences and advantages to their historic Guard counterparts and to active component soldiers of today. All 100th Missile Defense Brigade soldiers, regardless of their component, are on active-duty orders.

Guard soldiers who staff the Ground-based Midcourse Defense System are not burdened by consistent rotation through the brigade every one to two years like their active component counterparts. This allows these soldiers to stay with the unit and continue to conduct the mission for many years. Some have more than 10 years of experience on the system, a benefit not easily replaced. This is critical knowledge that gets passed down to new soldiers when they arrive at the unit.

The constant rotation of the 100th Missile Defense Brigade’s active component soldiers also provides valuable input to the operational crews and staff. The active component soldiers not only provide personnel trained and qualified to operate the system, but they also bring valuable insight into the broader Army air and missile defense community and missions across the world.

Once they leave the brigade, many of these same air and missile defense officers and NCOs go on to spread information about the brigade’s mission as they take up posts at missile defense batteries and air and missile defense coordination cells across the broader Army air and missile defense enterprise.

Complex System

The Ground-based Midcourse Defense fire control system is a complex system. The science on the technical side can be learned in three to six months after completing initial qualification and certification training, which itself can take three to six months. But the “art” of the system—being able to understand Ground-based Midcourse Defense fire control system behavior and better predict how the system will react to outside stimulus and operator input—is something that can take operators years, and hundreds of simulations, to fully understand. All Ground-based Midcourse Defense System operators, regardless of component, achieve that level of proficiency.

The threat the brigade’s soldiers face, particularly the missile defense crews at the 100th Brigade’s Missile Defense Element at Schriever Space Force Base and the 49th Missile Defense Battalion’s Fire Direction Center at Fort Greely, is potentially catastrophic to the nation. Because of this, crews are trained and certified to some of the highest standards in DoD.

The brigade has grown to include a permanent detachment of California Army National Guard soldiers at Vandenberg Space Force Base; a security detachment at Fort Drum, New York, to protect a ground-based interceptor in-flight communication system; and, in an administrative control relationship since 2020, the Colorado Army National Guard’s 117th Space Battalion, located at Fort Carson. The 49th Missile Defense Battalion’s Company A military police also now include a rotational platoon of Army National Guard MPs from various states to match the growth of the Ground-based Midcourse Defense missile defense complex at Fort Greely.  

Through the years, close coordination between the Colorado National Guard, Alaska National Guard and California National Guard headquarters, called the Ground-based Midcourse Defense “Tri-State,” has been an essential element in the success of the organization. National Guard soldiers typically remain within one state throughout their career.

However, for soldiers within the 100th Missile Defense Brigade to advance through increased positions of responsibility while staying within the enterprise so as not to lose their valuable training and skills, it is essential to have opportunities at other brigade organizations across the three states. The Tri-State organizations have hammered out various agreements to ensure interstate transfers are permitted, as appropriate, to allow for soldiers’ career progression.

The 100th Missile Defense Brigade and its subordinate units are unique among other DoD organizations and missions, given the niche in which they operate and the criticality of success. Hundreds of people, thousands of hours and millions of dollars go into maintaining the Ground-based Midcourse Defense System and training the missile crews. While it is never likely, it is always possible that the nation will come under ICBM attack.

If it does, U.S. security depends on fewer than a dozen missile crew soldiers on duty in Colorado, Alaska and California to get it right the first time in a matter of minutes. One hundred percent success is the only option for them, because even a partial failure means death and destruction on a scale not known in the American experience.

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Capt. Ronald “Beetle” Bailey, Colorado Army National Guard retired, has been a public affairs specialist with the U.S. Army Space and Missile Defense Command, Redstone Arsenal, Alabama, since 2018. Previously, he was a Ground-based Midcourse Defense operations officer and brigade historian with the 100th Missile Defense Brigade (Ground-based Midcourse Defense).