Japan's upper house of parliament approved a controversial security bill that would allow it to engage in defensive military action overseas in the event that the national security of its allies is severely threatened.

For the first time since the end of World War II, Japanese troops can deploy in overseas operations in a combat role in support of its allies; in other words, for collective self-defense.

Andrea Berger

Japanese Prime Minister Shinzo Abe's attempts to explain the change to domestic and international audiences have not gone smoothly.

He has faced opposition at home, with fist fights breaking out between lawmakers debating the bill.

In the wider region, China, which Japan perceives to be one of its greatest security threats, has raised the specter of a less-restrained Japan with possible nuclear weapons ambitions. China itself has nuclear weapons, making its first test 1964.

Chinese officials and experts have periodically tied Japan's reinterpretation of its military posture to the country's domestic nuclear capability in order to raise concerns that Japan could in future become more aggressive.

While it is reasonable to debate the new security bill, such insinuations are unwarranted. Here's why Japan is unlikely to ever build a nuclear bomb.

Since the 1960s, Tokyo has developed one of the most advanced civilian nuclear energy programs that exists amongst the international community.

That program generates approximately one third of the country's electricity at present, but could in theory also be used to produce material for use in a nuclear weapon.

Some assess that the scale and sophistication of Japan's nuclear infrastructure would enable it to build a nuclear weapon in a matter of months, should the unlikely political decision be taken to do so.

Strategic rival China has sought to draw attention to this fact, issuing loud warnings over Japan's stocks of nuclear material, for example.

But it should be noted that under the terms of the Non-Proliferation Treaty -- which Japan ratified in 1976 -- states are entitled to peaceful nuclear technology for energy purposes if they forswear nuclear weapons.

To ensure that the country's nuclear sites remain exclusively for peaceful use, they are subjected to intensive scrutiny by the International Atomic Energy Agency in Vienna.

The Agency consistently verifies the accuracy and completeness of Japan's declarations regarding its nuclear facilities, material, and activities and conducts monitoring and inspections at relevant facilities.

Its role in Japan will continue to be particularly important in order to dispel any fears that the country may harbor nuclear weapons intentions.

China and the International Atomic Energy Agency are not the only ones following Japan's nuclear activity closely.

Two other audiences are noteworthy.

The first is Japan's public, who have become increasingly wary of the risks and dangers associated with nuclear technology -- whether for civilian or military applications -- following the disaster at Fukushima in 2011.

The second is the country's closest ally, the United States, who is similarly attentive to the state of Japan's nuclear program.

In fact, it is because of Japan's alliance with the United States that the former has even less of an incentive to build a nuclear weapon.

In order to guarantee the security of Japan against major threats in its region, whether a militarily assertive China or a belligerent and nuclear-armed North Korea, Washington has vowed to respond to any serious armed aggression against Japan using whatever means necessary, including nuclear weapons.

By demonstrating the depth of its resolve to defend Japan, the U.S. hopes to deter any potential aggressors from attacking in the first place. U.S. troops stationed in Okinawa are a visible reminder of the alliance and the commitment that underpins it.

As long as Japan believes in the strength of the U.S.'s so-called "extended deterrence" guarantee it is unlikely to see any merit in having its own nuclear weapons capability.

For this reason, both countries work tirelessly to ensure the credibility and durability of their defence partnership -- an immeasurably important aim.

Despite what many may think, the Abe administration sees the new security bill as part of this broader effort to contribute to a two-way military relationship -- not as a legal green light for offensive action.

The bill creates the framework for Japan to give as much to the relationship as it receives, by enabling it to come to the aid of the United States if necessary.

More than anything else, history is likely to undermine any temptation Japan might have to build a bomb.

Japan was the first and only country to ever be attacked with nuclear weapons.

Over 100,000 Japanese citizens were killed in the August 1945 bombings of Hiroshima and Nagasaki.

Seventy years on, Japan's nuclear history will not be forgotten any time soon.

Indeed, it is because of that history that Japan has become one of the most active signatories of the Non-Proliferation Treaty.

Tokyo has invested significant resources into preventing the illegal spread of nuclear weapons-relevant materials and technology, promoting the conditions needed for nuclear disarmament, and reminding the world of the grotesque effects of the use of an atomic bomb.

The non-proliferation norm is one that Japan will have little incentive to abandon in the short, medium, or likely even in the long-term.

Contrary to the suggestions of some watching legislative developments in Japan, the new security bill is not going to change that.