The nuclear race is still on
Each year on August 6 the Japanese city of Hiroshima commemorates its destruction by an atomic bomb and reiterates a call for nuclear weapons to be banished.
But more than 70 years after that disaster, the odds on such a ban are slim as nuclear proliferation continues and the threat of a global tragedy hangs over the planet.
Although the bombings of Hiroshima and Nagasaki brought World War II to an end, atomic bombs soon became a key element in the US and Soviet arsenals, and a foundation for the Cold War that followed.
Four years after Hiroshima was devastated, the Soviet Union tested its first atomic bomb (A-bomb) on August 29, 1949. The United States had hoped to retain a monopoly over the new weapon for a decade and rushed to develop an even more terrifying warhead.
The US army tested the first hydrogen bomb (H-bomb) on November 1, 1952 but the Soviets were hard on its heels, detonating one of their own just a year later, in part owing to a spy network that sowed fear throughout the US population.
Both countries swiftly upgraded their nuclear arsenals and were joined by Britain, France and China, raising the number of warheads to fearsome levels.
By the late 1990s the United States had an estimated 10,000 nuclear warheads while the Soviet Union was believed to hold three times as many. It was only the collapse of the Soviet regime that allowed both countries to agree to a mutual reduction.
Despite France's tests in the Pacific, Hiroshima's mayor Takashi Hiraoka was able to deliver a "message of hope" on nuclear disarmament to 60,000 people who gathered for the 50th anniversary of the bombing in August 1995, including many who had survived the attack and helped rebuild an again prosperous city.
- New cold war? -
Such hopes have since been dashed with the emergence of several new nuclear powers, bringing the known number to nine.
Britain, France, China, India, Israel, Pakistan, Russia and the United States have nuclear weapons at their disposal, and North Korea has carried out several tests though it is not certain that it possesses operational warheads.
Iran is suspected of seeking to develop nuclear weapons and the non-proliferation treaty that took effect in 1970 is increasingly obsolete.
"Barring a major development or strategic surprise, we will have to get used to a world that includes at least nine nuclear states," notes Bruno Tertrais of the Foundation for Strategic Research.
And while the number of warheads has diminished, military arsenals continue to be developed with smaller tactical charges designed for cannons, for example, increasing the chances they could eventually be used again in combat.
In October 2016 Russian President Vladimir Putin scrubbed an agreement with the United States on weapons-grade plutonium disposal, a move described by independent military expert Alexander Golts as "a symbolic gesture that demonstrates that the sides no longer cooperate in this sphere." He added that it was not the first such agreement to be suspended.
At the start of 2014, nine countries, including North Korea, "possessed approximately 4,000 operational nuclear weapons," according to the authoritative Stockholm International Peace Research Institute (SIPRI). This would be enough to obliterate life on Earth several times over.
"If all nuclear warheads are counted, these states together possessed a total of approximately 16,300 nuclear weapons, compared to 17,270 in early 2013," it added.
For the past seven decades, the concept of mutually assured destruction (MAD) has kept fingers off the nuclear triggers. But the rise of bitter regional conflicts might upset that precarious balance.