Over the past year, the escalation of tensions between the United States and North Korea has caused much anxiety about the possibility of a nuclear war. Since the creation of the first nuclear bomb and the bombing of Hiroshima and Nagasaki, international diplomacy has focused its non-proliferation efforts on nuclear weapons.

In doing so, it has overlooked the proliferation of conventional weapons, which have killed millions since World War II and which continue to kill on a massive scale today.

As Amnesty International noted in a report released in late 2015, "reckless arms trading" encouraged atrocities committed by the Islamic State of Iraq and the Levant (ISIL) and other armed groups in Iraq. In 2016, more than 100,000 people were killed in conflicts in which conventional weapons were used.

And while the Nuclear Non-Proliferation Treaty has limited the new production of nuclear weapons, the world has experienced an uncurbed proliferation of conventional weapons with no effective international legal tools to control it.

Since 1960 - the early days of the Cold War nuclear arms race - international military spending has increased twenty-fold from $82bn to $1.69 trillion; and year on year, it continues to grow. While some of it goes to infrastructure maintenance and salaries for personnel, a significant part is spent on the acquisition of conventional weapons.

In 2015, the US, the country with the biggest defence budget in the world, spent $90bn of its $600bn defence spending on the procurement of conventional arms; it spent around $20bn on maintaining its nuclear arsenal.

The growing demand for conventional weapons is making many providers very wealthy. The top 100 arms companies have sold over $5 trillion worth of merchandise since 2002. In 2016, some $31bn was generated by the international arms trade, the US earning $9.9bn of it, followed by Russia with $6.4bn and Germany with $2.8bn.

Although there is no international law on how much can be spent on conventional arms, the Arms Trade Treaty (ATT) of 2014 sought to prevent weapons from being sold to countries that are under embargo or illegally transferred to state or non-state actors. According to the treaty, signatories should ensure the weapons they are selling are not going to be used in "terrorism", acts of genocide, crimes against humanity, serious violations of human rights, or the undermining of peace and security.

Unfortunately, over the years since its signing, the treaty has proven too weak to make a difference.

The first reason the ATT is failing is that the power of profit-seeking is trumping all other considerations. This is most evident with Saudi Arabia, which is currently the second largest weapons importer in the world. Although some countries like Germany have stopped selling weaponry to Riyadh - which stands accused of indiscriminate, reckless and wrongful targeting of civilians in the war in Yemen - others have not been able to resist the revenue to be made.

The UK, which has signed and ratified the ATT, made $1.5bn in 2017 selling arms to Saudi Arabia, while the US, which has signed but not ratified the treaty, made windfall deals worth potentially $110bn.

The second problem is that even if ATT signatories start implementing the commitments they made by signing the document, there are other countries that have either not signed or not ratified it, such as China, Russia, India and Iran. This means that a country like Myanmar, which is facing serious accusations of crimes against humanity, can still obtain a steady stream of weapons from some of these countries despite an ongoing European arms sales embargo.

Similarly with the war in Syria, despite strong evidence of war crimes by multiple parties, especially the Assad regime, countries such as Russia, Iran and possibly even North Korea, have not hesitated to sell weapons to Damascus. On the other hand, those fighting Assad have received weapons illegally re-routed by the US and Gulf countries from Eastern and Central European countries.

The above point highlights the other difficulty with the ATT - namely, that it primarily deals with legal transfers. The problem is that many conflicts are now fuelled by weapons supplied via illegal trade, especially in small arms. Although the size of this trade is estimated at being between 10 to 20 percent of the value of the legal arms sales, in some conflicts, illegal sources of weapons dominate the supply.

For example in Mexico, 70 percent of guns seized in the country and traced by the US Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) from 2009 to 2014 came from illegal transfers from the US.

In Afghanistan, the Taliban is buying large amounts of illegal weapons, including but not limited to hundreds of thousands of diverted US weapons.

This uncontrollable proliferation of conventional weapons will continue to take a heavy death toll each year unless the international community comes up with an effective international tool to control it - the way it did with nuclear weapons.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial stance.