EVERY state possessing nuclear weapons has difficulty answering the question, ‘How much is enough?’ It’s natural to think that more weapons will result in more security because nuclear weapons are so fearsome and because it’s hard to know what hand the competition is holding.

If the competition responds in kind, feelings of insecurity usually grow. Refusal to compete can also result in greater insecurity. Improved relations and nuclear risk-reduction agreements, tacit or otherwise, can provide a way out of this dilemma.

The guardians of Pakistan’s nuclear arsenal have achieved many successes, despite the efforts of the United States and export control regimes to prevent them. With an economy one-ninth the size of India, outside observers now believe that Pakistan is ahead of India in some nuclear weapon-related capabilities, including the size of its stockpile.

India is not, however, standing still. It, too, is increasing the size of its stockpile and flight-testing more advanced missiles. If New Delhi decides to pick up the pace of this competition, Pakistan will feel less secure as an unwanted arms race picks up steam.

Even if India chooses not to pick up the pace, Pakistan will become more insecure unless its economy and social cohesion improve. Nuclear weapons can help severe crises from becoming wars, and some kinds of added nuclear capabilities can strengthen deterrence.

But nuclear weapons cannot fix domestic ills, and if deterrence fails, the significant costs of acquiring nuclear weapons will become a mere down-payment to the extreme costs associated with their use.

The United States and the Soviet Union remain object lessons of how success can breed competition and insecurity. Both superpowers were guilty of wretched nuclear excess because their competition was always measured in relative, rather than absolute terms.

An adversary’s gains were always bad news, no matter how many weapons the home team possessed. The successful acquisition of ‘second strike’ capabilities — the ability to withstand a surprise attack and respond with devastating effect — never did relieve Cold War anxieties because the competition never waned, even at very high numbers. This twisted superpower dynamic only subsided when the Soviet Union failed because its economy couldn’t sustain the competition.

Three states with mid-sized nuclear arsenals — Great Britain, France and Israel — managed to avoid this dynamic because they didn’t have a nuclear-armed adversary in their approximate weight class, and because all three could rely on Washington as a back-up.

One key decision point for all states with nuclear weapons is whether to seek the means to deliver them at short, as well as longer ranges. Mobile missiles with longer ranges are easier for the home team to control in a crisis and harder for an adversary to target.

Short-range capabilities are the hardest to control because, in order to have maximum deterrent effect, they need to be positioned close to where battle lines might be drawn. These lines can change and can be breached quickly, especially with the use of air power.

The United States and the Soviet Union were never able to figure out how to secure short-range nuclear capabilities and to maintain command and control over them in the fog of war.

Nonetheless, the superpowers handed thousands of battlefield nuclear weapons to soldiers who would become victims of fallout from friendly as well as enemy fire. The Soviet Union planned to carry out a ground offensive across Europe with tactical nuclear weapons, while the United States planned to stop tank offensives with them. With the benefit of hindsight, these plans now appear to have been pure folly.

Huge Cold War arsenals of tactical nuclear weapons have shrunk considerably, but many still reside in Russian and US stockpiles. Success that leads to excess eventually results in reductions — long after it becomes clear that the risks associated with tactical nuclear weapons far exceed their military utility.

Pakistan and India won’t compete as foolishly as the United States and the Soviet Union, but they are still entering uncharted territory. This territory is even harder to map because Chinese strategic capabilities figure in New Delhi’s nuclear requirements, and because all three countries maintain secrecy over their holdings. A triangular competition makes it even harder to determine how much is enough.

As the conventional military balance tilts in India’s favour, Pakistan has signalled a requirement for short-range nuclear capabilities to strengthen deterrence against the threat of Indian retaliation after dramatic attacks by violent extremists based in Pakistan.

New Delhi might also seek short-range nuclear capabilities, if it decides not to rely on longer-range missiles and airpower. Other new aspects of the competition are emerging with cruise missiles and sea-based nuclear capabilities. The question, ‘How much is enough?’ is being answered in ways that Pakistan and India are unlikely to find reassuring.

The writer is co-founder of the Stimson Centre.