For Osama bin Laden, who spent years in seclusion with little to do but devise new ways to kill Americans, the first big plans to emerge from his compound paint a picture of a terrorist who stuck to what he knew best and what worked before: planes,trains and ships.

The computer files hauled from his hideout in Pakistan have provided intelligence officials with an unparalleled glimpse into the mind of al-Qaeda's founder. But perhaps most surprising about the first two attack scenarios to surface in those documents is just how predictable they were.

He hoped to attack trains, just as terrorists had done in Mumbai and Madrid. He retained his fascination with attacking airplanes. And, according to U.S. officials and a law enforcement bulletin Friday, he wanted to hijack oil tankers and blow them up at sea.

The fact that they were old ideas made them no less deadly. Yet with no specific plan in motion and after so many warnings about similar plots over the past decade, the revelations were met with little more than a shrug by many in the security business. Oil prices weren't affected; shippers said it was business as usual.

"This is nothing new," said Christopher Davidson, a professor of Middle East politics at Durham University in northern England. "This is just confirmation of what most security and terror analysts had guessed."

In short, bin Laden wanted to attack just where the United States figured he would.

Billions spent on intelligence

Part of that is due to the billions of dollars that the U.S. has spent on intelligence and security since the attacks of Sept. 11, 2001. So much has been spent on secret wiretaps, satellite surveillance and new spies and analysts that the U.S. isn't supposed to be caught by surprise. Anything less than foreseeing and preventing an attack is a failure.

But the predictability of bin Laden and his commanders is one reason why the core group of al-Qaeda is no longer the gravest threat to America. That has fallen to the

al-Qaeda affiliate in Yemen, where operatives have proved more clever and nimble than the terror group's founders, now forced deep into hiding by CIA drone attacks.

The Yemeni group has come perilously close to carrying out two major attacks on U.S. targets. In the first, the group stitched a bomb into a terrorist's underwear on Christmas 2009 and outsmarted years of airline security improvements. Passengers on the Detroit-bound flight subdued the suspected bomber. Authorities believe his sweat interrupted the bomb's chemical reaction.

The second was last year's attempted bombing of U.S.-bound cargo planes. The bombs were shrewdly wired into printer cartridges, which passed unnoticed through security. The bombs nearly went off before intelligence officials, acting on a tip, discovered and defused them.

"The organization has a very fast learning curve, quickly adjusts and improvises, and is very adept at exploiting opportunities," Christopher Boucek, a scholar at the Carnegie Endowment for International Peace, told the U.S. Congress in March.

Military hierarchy

Before Sept. 11, al-Qaeda was made up of veterans of the Afghan guerrilla war against the Soviet Union. The hierarchy was military in nature. Attacks originated with the leaders or were approved by them.

Al-Qaeda in Yemen is younger and less committed to such a rigid structure. Its master bombmaker, Ibrahim al-Asiri, is 29. The country's top al-Qaeda commander, Nasser al-Wahishi, is 34. Anwar al-Awlaki, the American-born cleric who has become a leading figure in the organization, is 40.

Bin Laden was 53 and had spent the past several years holed up in a walled compound in Abbottabad, Pakistan, when U.S. Navy SEALs killed him this month. His likely successor, Ayman al-Zawahri, is 59.

Bin Laden's writings show that, to the end, he remained committed to carrying out spectacular attacks on high-profile targets. The Yemeni branch has embraced the idea of recruiting terrorists over the internet, providing them with bombmaking instructions and letting them pick their own targets.

Bin Laden liked symbolic targets and dates. Al-Qaeda in Yemen has selected targets of convenience. The suspected Christmas bomber, for instance, picked Detroit only because it was the cheapest ticket.

Newcomers innovate

That's why the question of who will replace bin Laden is also a question about the future of al-Qaeda. Will it continue to try for massive strikes on the biggest, most predictable targets or will it look for ways to be more nimble? Which is worse for the United States?

Michael Leiter, director of the National Counterterrorism Center, alluded to this in February when he told Congress that bin Laden and his cohorts in al-Qaeda's core had been weakened.

"I think, to some extent, that's quite good. It reduces the likelihood, again, of a large-scale organized attack," he said. The bad news, he said, is that "it allows the franchises to innovate on their own."

An innovative al-Qaeda is less predictable and arguably more dangerous, he said: "They've been quite successful at being innovators that make our jobs more challenging."