Here are how the numbers of active duty military personnel have fluctuated over the past 60 years.1

The numbers for all services spiked in 1968-69 as U.S. involvement in the Vietnam War reached its peak. All dropped dramatically as that war drew down. But even the peak of the Vietnam War pales in comparison to World War II. In 1945, there were over 12 million active duty military personnel.

The Army, Navy, and Air Force had significant cuts in the numbers of personnel with the end of the Cold War, while the Marine Corps numbers have stayed relatively flat.

Total Active Duty Military Personnel

Army

The Army has the most personnel of any of the U.S. armed services. Like the Marine Corps, its core strength lies in the prospect of boots on the ground. Technology can certainly help boots on the ground be more effective, but numbers matter.

And a large number of front-line troops means an even larger number of support personnel.

In the mid-1950s, the Army was demobilizing from the Korean War. It ramped up again sharply for the escalation of U.S. involvement in Vietnam in the second half of the 1960s, before a rapid dropoff by the early 1970s as the the United States withdrew from Vietnam.

From the late 1980s to the mid-1990s, with the end of the Cold War, there was another significant reduction of nearly 40 percent. Since then, aside from a relatively small percentage bump for the so-called surge in Iraq around 2007, the number have hovered at around 500,000.

Navy

The numbers of Navy personnel have mostly declined over the past 60 years, although the reductions have been neither as sustained nor as deep as those of the Air Force.

Like the Air Force–although perhaps to a somewhat lesser revolutionary extent–the Navy has benefited from technological developments over the past 60 years. The Navy’s capabilities have also evolved over that time to encompass air power and even ground power.

That broad spectrum of options is paired with a high degree of mobility. The Navy is no longer confined to patrolling the high seas. And sending a carrier to a troublespot projects immense power relatively quickly without the time and bureaucracy involved in negotiating base agreements or flight corridors.

Marine Corps

Like the Army, the Marine Corps’ defining feature is its ability to deploy boots on the ground in troublespots.

With its emphasis on mobility and agility, the Marine Corps has benefited from policymakers’ increasing preference for those qualities.

More than any of the other services, the Marine Corps has been able to maintain relatively stable personnel numbers (aside from a spike during the Vietnam War).

Air Force

Since the Air Force’s heyday in the 1950s, with the buildup for the nuclear age and the emphasis on strategic deterrence aimed at the Cold War enemy, the Soviet Union, the number of Air Force personnel has declined steadily since. More than any of the other services, its trend in personnel numbers is one of decline. The manpower force levels today are just over one third of what they were in the 1950s.

While some of the explanation for that comes down to shifting emphasis and the endless competition for Defense resources and funding, much of it comes down to the massive shifts in technology over the past 60 years that have revolutionized Air Force power. Missiles, computers, more effective airplanes and weapons, satellites, and even drones have all meant that over the past 60 years Air Force effectiveness has relied less and less on sheer numbers of personnel.

U.S. Military Personnel 1954-2014: The Numbers