America’s nuclear shield may not be as secure as Trump says

Recent articles highlight deficiencies in system used to protect against nuclear attack

President Donald Trump and other US officials recently expressed great confidence in the capability of the American Ground-based Midcourse Defence (GMD) system, America's only guard against incoming intercontinental ballistic missiles (ICBMs) carrying nuclear warheads. However, in a disturbing article in Scientific American, June 2019, nuclear weapons security analysts Laura Grego and David Wright report that the GMD system is very unreliable and vulnerable. They conclude that the GMD system offers only minimal protection while adding to global nuclear risks.

Nuclear weapons are one of the great shames of our age. Beginning in the 1950s, a nuclear weapons race developed between the two superpowers America and the Soviet Union. Each side frantically accumulated nuclear warheads in an attempt to develop a crippling first-strike capacity, so powerful it would prevent a retaliatory nuclear strike.

By 1986, total warhead numbers between the two superpowers had risen to 60,000. These huge warhead numbers also constituted a form of deterrence against nuclear war because the almost certain likelihood of a retaliatory strike would result in “mutually assured destruction” (MAD – a perfectly apt acronym) of both protagonists.

Acknowledging the craziness of the situation, US and Soviet leaders eventually signed the Strategic Arms Limitation Treaty in 1972. They also signed the Anti-Ballistic Missile (ABM) treaty, limiting defence against long-range missiles and breaking the cycle of perceived improvements in defence by one side sparking improved offensive capacity on the other side. Stockpiles of nuclear weapons dropped from 60,000 in 1986 to 10,000 today.


America and USSR signed a further Intermediate-range Nuclear Forces Treaty (INF) in 1987 banning the use of nuclear and conventional ground-launched ballistic missiles with ranges of 500 to 5,500 km.

September 11th

But everything changed after the terrorist attack on the Twin Towers on September 11th, 2001. Defence against external threats assumed paramount importance and arguments for a cautious approach to missile defence were ignored.

In 2001 then US president George W Bush announced the US would withdraw from the ABM Treaty and the US government decided to rush ahead with the GMD missile defence system.

The authors describe how GMD defence works. ICBMs bearing nuclear warheads launch thousands of kms from their targets and accelerate (boost phase) within minutes to a speed of 25,000 kms per hour. They then release multiple warheads that arc through space for about half an hour (mid-course flight), then enter the atmosphere and descend towards their targets (terminal flight phase). GMD defence efforts focus on the mid-course flight – GMD defence interceptor missiles crash into the warheads thereby “killing” them.

However, Grego and Wright claim that development of this new GMD system was fast-tracked so quickly it by-passed many traditional Pentagon checks and oversights (“fly before you buy”) that ensure defence systems work reliably before being put in place.

Amazingly, the authors report that the GMD interceptors have destroyed their targets in only half the tests conducted to date. Furthermore, these tests were easier tasks than GMD would encounter in real attacks when countermeasures would be taken by the enemy. In other words, if a real nuclear attack were mounted today, the current GMD defence system would allow some nuclear warheads through to target.

The situation seems to be in a right mess. Although the GMD system is not fit for purpose, American politicians and policymakers think it is. This could encourage US leaders to take more risks in foreign policy. At the same time foreign aggressors will be tempted to believe some of the hype about the GMD and intensify efforts to develop more offensive weapons.

Both authors of this Scientific American article are members of the Union of Concerned Scientists, a US-based science advocacy organisation that some critics believe is more interested in activism than in science. Perhaps the authors exaggerate the deficiencies of the GMD system? But I think not. They quote department of defence publications to back their GMD test-failure statistics and it seems to me there is merit in their criticism.

Ominously, the INF Treaty signed in 1987 just foundered on August 2nd last. The grim spectre of the mushroom cloud hung over everybody from the 1960s through the 1980s and didn’t significantly fade until the breakup of the Soviet empire, starting in 1989. We certainly don’t want to blunder back under that mushroom again.

William Reville is an emeritus professor of biochemistry at UCC