Changing the U.S. strategy for fighting terrorism in a post-Osama bin Laden world will be key to finding a way to reduce defense spending. The first step to that change is an up-to-date analysis of the threats that we will face over the next 10 years.

Defense Secretary Leon Panetta on Thursday gave Pentagon reporters his view of “what national defense is all about.” He said, “The fundamental issues we have to deal with are to identify what those threats are and make sure that we’re prepared to confront those threats.”

Let’s face it, the big jump in Pentagon spending in the almost 10 years since Sept. 11, 2001 — from $432 billion in fiscal 2001 to $725 billion in fiscal 2011 — has been fueled primarily by President George W. Bush’s war on terrorism, which not only generated billions in increased spending on homeland security and foreign intelligence-gathering, but also more than $1 trillion to invade and then attempt to pacify and reconstruct Afghanistan and Iraq. Some financial commitments from those actions will last years.

Those of us who covered the Cold War remember not only the costs in lives and the financial price tag of two un-won conflicts, Korea and Vietnam, but also the spending of hundreds of billions on what became a politically driven arms race. That race bought us more than 10,000 nuclear bombs and missile warheads, most of which will now cost billions to dismantle.

So, what realistically are the terrorism threats over the next 10 years? And what does the United States need to do to be “prepared to confront those threats,” as Panetta put it.

In recent weeks there have been many “expert” views about the terrorism threat, both foreign and domestic. Panetta helped start the debate when he told reporters on July 9 in Kabul, “We’re within reach of strategically defeating al-Qaeda.” Last week he described a “badly damaged al-Qaeda,” but said it remains a threat “to conduct attacks in this country,” as are terrorist networks spawned by bin Laden’s example.

The post-bin Laden terrorism threat was a major subject at the Aspen Institute National Security Forum two weeks ago.

Michael Leiter, former director of the National Counterterrorism Center, which serves as the primary fusion center for all foreign and domestic terrorism information, said that what’s left of core al-Qaeda in Pakistan remains a threat, along with other violent anti-American extremists in that country. He also said people in Yemen, Somalia and East Africa pose threats, though not of the 9/11 type.

But, Leiter warned, even unsuccessful attacks “have a psychological effect that would be very real.”

At another Aspen session, former CIA deputy director John McLaughlin warned that although drone strikes have “thinned out their ranks,” and al-Qaeda’s Ayman al-Zawahiri is not an inspirational leader, he nevertheless is “disciplined, tough, has street and Afghan war credentials and was a member of the Egyptian mafia.”

Asked how it could be known that terrorism has been defeated, McLaughlin pointed out that there have been terrorists since biblical times. But he drew an interesting Cold War parallel, saying the threat from terrorism could become like that from communism. He said there “are still communists in the world, but no one believes in communism.” As for terrorists, when they are “a nuisance” and “not a deadly threat,” the war on terrorism could be considered over.

Charles Allen, a longtime CIA officer who most recently ran the intelligence operation as undersecretary of the Department of Homeland Security, made sense during that same Aspen panel when he talked about using risk management to help allocate federal money to meet terrorism threats.

It came up when he fielded a question about the hundreds of thousands of soft targets, such as malls and movie theaters and football games. “We have to take risks; we cannot continually spend money on every conceivable risk or scenario,” Allen said.

Both Allen and Leiter brought up the idea that President Obama, though he took a bold military step in authorizing the raid that killed bin Laden, also has shown interest in increasing the nonviolent and less costly approach to terrorism through counter-radicalization programs. Allen told his audience that a new administration-coordinated counter-radicalization program is due out soon.

Leiter said that such programs help, but that they don’t go well when the Pentagon is “the big dog” conducting them.

But Leiter’s remarks at the Aspen event point to the reason why Americans, over-concerned about their security, historically have overspent on defense.

With the death of bin Laden, Leiter said he expects to see more al-Qaeda-inspired terrorist attempts. “The American people need to understand at least small-scale attacks are with us for the foreseeable future,” Leiter said, adding that it would be difficult to stop them all.

The way to “fundamentally defeat that threat — which is very difficult to stop in its entirety — is to maintain a cultural resilience,” Leiter said. That means, he said, the public, politicians and particularly the media must respond by not playing up the attack , so “we are not delivering victory to our enemies that otherwise they would not enjoy.”

Leiter said that although the terrorism threat today is real and there will be future tragedies in which people die, it is not “an existential threat to our society,” and “our basic principles that have held our country together . . . can continue to do so unless we overreact to this threat in a very unhealthy way.”