WASHINGTON -- The Army has experienced fundamental, generational change in the past four years under the leadership of Chief of Staff Gen. Mark A. Milley.

The general turned over the reins of America's senior service in a ceremony Aug. 9 to Gen. James C. McConville. The Senate has confirmed Milley to succeed Marine Corps Gen. Joe Dunford as chairman of the Joint Chiefs of Staff at the end of September.

Milley spoke about his term as chief of staff in a wide-ranging interview in his now empty office.

When Milley became chief of staff in 2015, the Army was suffering through readiness shortfalls. While individual units going into harm's way were well-trained, well-led and well-supplied, the combat effectiveness of the organization as a whole was in a trough. "The Budget Control Act and sequestration hit training and maintenance accounts hard," Milley said.

Continuing resolutions, government shutdowns and curtailed budgets meant that services had to apportion money to those units heading to Iraq or Afghanistan. The current fight was funded, but the potential future force was not.

"I came in with a different vision, a different look, and I intended to make some fundamental changes from the very beginning," the general said. "But the bottom line is you can have all the fundamental ideas you want, but unless thousands of people buy into those ideas, they aren't going anywhere. These people have taken the ideas, operationalized them and put them in place. Without them, we aren't doing anything. This is a team of teams that make things happen."

The Army is a large organization with three components -- active duty, the Army National Guard and the Army Reserve -- and the Department of the Army has about 300,000 civilian employees and hundreds of thousands of family members. Retirees also are part of the service.

Changing anything in the service takes time, Milley said, and the tenure of one chief of staff is not enough time. But the changes needed to be made, he said, adding that these fundamental changes in the U.S. Army are necessary because the strategic environment itself has shifted.

"The character of war has changed. Not the nature of war -- the character," Milley said.

When he talks of this concept, he is talking about where the fight occurs, how the forces fight, what doctrine applies, what weapons are needed and what organization is best suited. The character changes over time. Warfare changed when someone developed stirrups and it became practical for soldiers to ride horses into battles, the general said. The development and fielding of repeating rifles, of barbed wire, of wheeled vehicles and airplanes all changed the character of war, he explained.

All militaries in the world understand this to a greater or lesser extent. "Us, the Chinese, the Russians and others are moving in directions to shape ourselves, to adapt to this world," Milley said.

The changes are as great as the ones faced by soldiers following the end of the Vietnam War in the mid-1970s. The introduction of precision-guided munitions, the internet, and the widespread and prolific use of computers and information technology really enabled the changes, Milley said.

Added to all this is the broad, almost ubiquitous, deployment of sensors around the world. Pretty much the whole world is "sensed" by something, the general said. New technologies such as hypersonics, robotics, artificial intelligence, supercomputing and the cloud accelerate this changing world.

Changing demographics also forces the changes in the character of war. These changing demographics reach back to the dawn of the Industrial Revolution, when farm workers moved to the cities for opportunities. This process continues. The majority of people worldwide no longer live in rural areas, Milley noted. Today, about 55 percent of the people on Earth live in urban environments. The United Nations estimates that will rise to 66 percent by 2050.

"If that's true, and the nature of war is an extension of politics, and you are trying to impose your will on your opponent, then it stands to reason that the geography of warfare will shift toward dense urban environments," Milley said. The U.S. Army needs to be able to operate and win on this new battlefield.

Milley's priorities predated the National Defense Strategy. That document took many of these ideas and applied them across the services. The biggest change was the return of global competitors China and Russia. "[The Army] had to sustain and continue for as long as the country needed the counterinsurgency and counterterrorism fight, while shifting to be able to deal with rising great power competition," he said. "So we had to do two things at once: 1, significantly improve the readiness of the current force, and 2, set the institution on a path to modernize so it would be able to fight a near-peer competitor."

Milley said history really doesn't repeat itself, "but it rhymes a little bit." Army Gen. Creighton Abrams served as the chief of staff after Vietnam. He was faced with the rising challenge from Soviet Union, and he laid the groundwork for all that followed: AirLand Battle, the Big Five Army weapons and so on, the chief said.

Milley said he needed to improve readiness of the force immediately. He also needed to begin the work of "seeing the future and modernizing the Army to meet that."

At the same time, he was facing calls for drastically reducing the size of the service, with some experts saying the regular force should go below 320,000. Milley and the various Army secretaries he served under worked with Congress to explain the repercussions of such a drastic cut and was able to get that reversed.

The international order that has maintained peace among great powers is under intense stress from Russia, China, North Korea, Iran, and terrorists. It is under stress in the West as well, with rises in populism and nationalism, the general said. "We should operate with realism and restraint," he said. "But fundamental to that is strength. A strong and capable U.S. military able to deploy quickly is one of the greatest guarantors of world peace."

Milley instigated other major changes, including increasing infantry training to 22 weeks -- the first major revision since World War II. He anticipates similar increases in training for other combat specialties. Other changes include:

• Establishing security force assistance brigades to professionalize Army training of partner militaries;
• Standing up Army Futures Command to ensure that the capabilities the service will need will be there;
• Prioritizing the capabilities most needed by the service and ensuring funding apportioned was based on this priority list; and
• Taking on a full slate of family issues looking at housing, credentialing, child care, exceptional family member programs and more.