Too often, opponents of robust missile defenses portray nonproliferation measures as an easy substitute or alternative as if the two were mutually exclusive.
Properly understood, combating proliferation and missile defense policies should be viewed as complementary components of a defensive deterrent.
Nuclear weapons technology has advanced considerably over the past six decades, but the basics of atomic physics have remained the same since American and German scientists detonated the first weapon in 1945.
The knowledge of how to create primitive nuclear weapons is less an issue for nonproliferation policy than are the materials to make them.
The story of Abdul Qadeer Khan, whom former CIA Director George Tenet once called "at least as dangerous as Osama bin Laden," provides important lessons for how to think about intelligence and ballistic missile defense in the post-Cold War, post-9/11 security environment.
Experienced in uranium enrichment from years of working in the Netherlands, Pakistani national A.
Q.
Khan returned to his homeland in the 1970s to become the father of the Pakistani nuclear weapons program.
The program resulted in nuclear detonations in 1998, for which Khan became a national hero.
To enrich uranium for Pakistan, Khan created a web of front organizations and workshops in numerous countries across four continents to circumvent international export controls and acquire gas centrifuges, which are commonly used to enrich naturally occurring uranium.
As Director General of the International Atomic Energy Agency Mohamed ElBaradei described it, "Nuclear components designed in one country could be manufactured in another, shipped through a third (which may have appeared to be a legitimate user), assembled in a fourth, and designated for eventual turnkey use in a fifth.
" Pakistan detonated its first nuclear weapon in 1998.
Once in place, the Khan network also proliferated nuclear designs, centrifuges, and technologies to other countries.
Khan visited 18 countries between 1997 and 2003 and sold centrifuges and other technologies at least to Iran, North Korea, and Libya.
Iran seems to have received centrifuge assistance as early as 1987.
North Korea reportedly purchased centrifuge designs and sample centrifuges.
Libya was Khan's biggest customer, ordering an enormous gas centrifuge plant capable of producing enough highly enriched uranium to build 10 nuclear weapons per year.
Some of the nuclear weapon designs discovered in Libya came indirectly from China by way of Khan's operatives.
Khan's network operated largely undetected during the 1980s and 1990s.
Intelligence services failed to penetrate it until 2000, and the network was not publicly exposed until October 2003.
Only after this exposure did Pakistan interrupt Khan's operation.
After he was arrested in February 2004, he confessed to sending centrifuges to Libya, North Korea, and Iran, but the Pakistani government pardoned him, although he remains under house arrest.
What is certain is that a considerable degree of proliferation succeeded despite intelligence efforts to discover it.
As it relates to missile defense, this episode teaches that: Effective nonproliferation cannot be sacrificed to formal arms control.
The Bush Administration's exposure of the Khan network in 2003 is one of the biggest nonproliferation revelations in history.
Less aggressive and more formal efforts in the 1990s allowed the network to go unnoticed and put too much faith in the Nuclear Non-Proliferation Treaty and other such parchment barriers.
Intelligence fails.
The fact that the Khan network existed undetected for decades constitutes an extraordinary failure of the intelligence community and sounds a cautionary note against relying too heavily on either intelligence or nonproliferation efforts.
We still do not know exactly what materials Khan passed along, when he did so, or to whom he sent them.
Proliferation can be policy.
It is often assumed that regimes are responsible enough that they would never transfer technology to bad actors.
It is also assumed that any such transfers must be done by individuals acting on their own and that, acting alone, they would not have the resources to do much damage.
But the idea that A.
Q.
Khan was coordinating the world's most extensive proliferation network across multiple regimes without the knowledge of the government officials who paid him is simply beyond belief.
The U.
S.
Department of State regularly sanctions Chinese and Russian state-owned companies for transferring technologies and material to rogue regimes in violation of international agreements.
Bad ideas have consequences.
We have seen that intelligence services are fallible and that determined states and individuals can achieve in the 21st century what American and German scientists achieved in the 20th century.
Therefore, missile defense and other active defenses have become even more essential.
The fact is that nonproliferation is not enough.
The consequences of not aggressively pursuing nonproliferation are too high, but the consequences of neglecting more active missile defense are also too high, especially if the next A.
Q.
Khan is more successful in selling to rogue regimes the tools they need to fulfill their nuclear ambitions.
In the short term, nonproliferation efforts can lead to important successes when coupled with a credible threat to disarm by force if necessary, as with the case of Libya.
In the long term, however, the 1940s technology and knowledge will leak out.
The knowledge of nuclear physics has proliferated worldwide.
The controlled fission of radioactive atoms has long been the basis for clean and reliable energy, and nuclear energy may yet experience a renaissance, further expanding both our knowledge about and the availability of nuclear material.
By raising the cost for would-be adversaries to acquire weapons of mass destruction and by reducing the certainty that these weapons could be delivered on target, nonproliferation and missile defense together can deter rogue regimes from investing in nuclear weapons and delivery systems.
The most important lesson from the Khan story is that nonproliferation should not be pursued in the absence of more active defenses against such weapons.
A national security strategy that neglects to plan for the day when nonproliferation fails-at the expense of an attack on an American city-is not much of a strategy.