WASHINGTON — The U.S. Defense Department several years ago began to shift its focus away from defending U.S. territory against long-range strategic missiles to a more flexible theater-based approach, and the new direction has received surprisingly strong domestic and international support, a top Pentagon official said March 22.

With the wind at its back, the U.S. Missile Defense Agency (MDA) must now concentrate on building and deploying missile defense assets as quickly as possible, while increasing the use of open standards and interoperability among these systems, U.S. Marine Corps Gen. James Cartwright, vice chairman of the Joint Chiefs, said at the U.S. Missile Defense Conference here.

In 2002, then-U.S. President George W. Bush announced the nation would develop and deploy a system to defend the United States against rudimentary long-range ballistic missile attacks from so-called rogue states like Iran and North Korea. The Pentagon quickly began fielding and testing ground-based interceptors in Alaska and California, with mixed results. The Bush administration also made plans to deploy ground-based interceptors in Europe to defend allies and deployed forces from the Iranian threat.

In the years that followed, the global proliferation of long-range strategic missiles progressed more slowly than expected, while the number of nations with short- and medium-range ballistic missile capabilities grew. MDA budgets in recent years have increased spending on theater-based missile defense systems such as the Aegis Ballistic Missile Defense and Terminal High Altitude Area Defense systems.

The administration of U.S. President Barack Obama announced in September a shift in strategy for the European missile shield that will be based on the Standard Missile-3 interceptor, which will be deployed on Aegis ships in European waters and at least one ground site in Romania.

“I would never have thought that between last year and now that we’d be sitting here with a program that has broad global support, broad national support [and] bipartisan support on the Hill, which for my scar tissue is going to take some healing but it’s a good thing,” Cartwright said. “And now we’re really in a mode of, ‘How fast can we produce?’”

The major decisions being hashed out now inside the Pentagon are related to looking at the entire force structure, including offensive and defensive capabilities, and finding the right balance between the two.  With actors ranging from the individual terrorist to a nuclear-armed peer competitor, the strategic environment is more complicated than ever, and missile defense has to fit in with other capabilities including the nation’s ICBM fleet and next-generation strategic bomber.

“Heretofore, quite frankly, we have done most of our modeling and simulation in isolation,” he said. “What if I had to defend the world with missile defense only? How many rounds do I need? The numbers add up to unobtainium. We’ve got to understand what the balance is. We’ve got to understand what our enemy believes will change the way that he behaves. … We have to have enough defense to know what the situation is and to hold our own while we bring offensive power to bear.”

For the future of ballistic missile defense, the key will be cooperation with allies, Cartwright said. The United States already has cooperative development programs such as the Arrow interceptor system with Israel and a larger version of the Standard Missile-3 with Japan. The future of missile defense will lie in jointly operating these systems using a command-and-control suite that can bring in technologies built by any nation.

“We can’t do this all ourselves,” he said. “We can’t do the defense all ourselves, and we certainly can’t do the offense all ourselves. We’re going to have to work it as coalitions. … It may be all that you do is share warning in some cases. But it’s time to start sharing that warning because that will lower the threshold for those who would want to do harm. That will change the calculus of the conflict.”