Just after midnight, in a secret bunker outside Moscow, the warning sirens began to blare. A simple, ominous message flashed on the bunker’s main control panel: Missile Attack!

It was no drill. A Soviet satellite had detected five U.S. nuclear missiles inbound.

The control computer ordered a counterstrike, but the bunker commander, a nerdy lieutenant colonel named Stanislav Petrov, acting on a hunch, overrode the computer and told his Kremlin superiors it was a false alarm. The Soviet brass quickly stood down their missiles, saving 100 million Americans from nuclear incineration.

This brush with Armageddon happened more than two decades ago, but nuclear missiles are still on hair-trigger alert in Russia and the United States. Today, they may be even more vulnerable to an accidental or renegade launch than they were in Petrov’s day.

“The security of both nations should not be dependent on the heroic act or good judgment of a single individual,” said Sam Nunn, the former senator from Georgia.

Long active in anti-proliferation efforts such as the Nuclear Threat Initiative, Nunn is leading a campaign to persuade U.S. and Russian leaders to take their thousands of strategic nuclear warheads off hair-trigger alert, a status that remains in effect more than a decade after the Cold War ended.

“The chances of a premeditated, deliberate nuclear attack have fallen dramatically,” Nunn said in an interview with Knight Ridder. “But the chances of an accidental, mistaken or unauthorized nuclear attack might actually be increasing.”

In his 2000 election campaign, President Bush called the hair-trigger status “another unnecessary vestige of Cold War confrontation” that creates “unacceptable risks.”

The first Strategic Arms Reduction Treaty, which took effect 10 years ago this month, doesn’t address hair triggering. Nor does the Treaty of Moscow, which Bush signed with Russian President Vladimir Putin in 2002 to reduce the size of the U.S. and Russian strategic nuclear arsenals.

Nunn believes the hair-trigger status has become “the most dangerous element of our force posture.”

A hair trigger means missiles are launched – either from land or sea [i.e., Trident] – upon the warning of an attack. That is, within about 15 minutes of a confirmed warning. In theory, the assurance that a retaliatory attack would be launched before the missiles could be destroyed would deter either country from trying a nuclear sneak attack.

“This is the logic of the Cold War – Mutual Assured Destruction,” said Daniil O. Kobyakov, a nuclear expert at the PIR Center, a policy studies institute in Moscow. “De-alerting requires a change in rationale. There’s still a certain inertia on both sides.”

Nunn and others see that inertia in the Bush administration’s refusal to consider the Comprehensive Test Ban Treaty and its request – since defeated in the Senate – for some $500 million for research on a so-called “bunker buster” nuclear weapon and low-yield “mini-nukes.”

Russia, too, has some Cold War inertia to overcome. Putin proudly announced last month that Russia was testing “the newest nuclear missile systems … that other nuclear states do not have.” He offered no further details about the weapons.

A number of political analysts believe Putin’s comments – which were unprepared remarks made to a group of senior commanders at the Ministry of Defense – were intended to boost military morale and for domestic political consumption.

“I’m sure it was nothing surprising to the U.S.,” said Kobyakov, noting that the Strategic Arms Reduction Treaty obliges each side to provide technical data on any new nuclear weapons.

Kobyakov and others believe Putin was probably referring to the Topol-M missile, which has long been in the Russian pipeline, and a sea-launched missile that’s being developed. There are rumors in military circles in Moscow that the new missile could be maneuvered in flight, unlike current ballistic missiles, to foil the Bush administration’s planned national missile defense system. One senior Russian general cryptically called it “a hypersonic flying vehicle.” Government officials in both countries are keen to point out that they’ve stopped targeting each other with their nuclear missiles, although experts say this “de-targeting” is political hokum.

The old targeting data and missile trajectories are stored in command computers, Kobyakov said. And missiles can be re-targeted in a matter of seconds: A couple of mouse clicks on a computer would put Washington, Miami or Moscow back in the nuclear crosshairs.

But it’s the danger of accidental or maverick launches that most concerns atomic experts. That danger is heightened, in part, by the decrepit state of Russian defenses.

“The Russian Early Warning System is essentially useless,” said Theodore Postol, a professor at the Massachusetts Institute of Technology and an expert on early warning issues and technology.

Holes in Russia’s satellite and radar networks, Postol said, mean U.S. submarines in the North Atlantic can strike Moscow with a two- or three-minute warning for the Russian capital. Launches from the North Pacific could hit the city with no warning at all.

Postol also said a new Prognoz satellite warning system “may never be in place.”

Stanislav Petrov, the old bunker commander, the man who saved America back in 1983, nodded his head sadly when told of Postol’s assessment.

“That’s right, not enough satellites,” he said. “We never had enough.”