Big changes are in store.

The first is the imminent departure of Barack Obama as president of the United States. Eight years ago, Obama, in a landmark speech in Prague, declared “America's commitment to seek the peace and security of a world without nuclear weapons.” He will leave office on Jan. 20.

Obama’s successor, who also will control America’s launch codes for nuclear weapons, is Donald Trump. Recently, the president-elect posted a tweet that said, “The United States must greatly strengthen and expand its nuclear capability.”

His tweet alarmed many people, as it signaled a radical departure from the Obama administration’s nuclear arms policy.

But there must be no turning back on the path toward “a world without nuclear weapons.”

This year will mark the start of multinational negotiations for a treaty to ban nuclear arsenals. This opportunity should be taken to create a powerful global movement toward a future free from nuclear weapons. Japan should play a prominent role in promoting this concept.

OBAMA'S LEGACY

There is no disputing the efforts Obama has made to tackle the threat posed by nuclear arsenals.

He used his leadership to organize four nuclear security summits to discuss how to thwart terrorist attacks involving nuclear materials. These conferences contributed significantly to efforts to exert stricter management of nuclear substances as they helped him and other world leaders to share a deeper understanding of the problem.

In 2015, Obama helped work out an agreement between Iran and leading world powers on curtailing Tehran's nuclear development program, which had been a key international security issue for many years.

Last year, Obama became the first sitting U.S. president to visit Hiroshima, which in 1945 became the first city to be leveled by atomic bombing.

None of these achievements was possible without Obama’s strong personal commitment to the cause.

Saying this, however, doesn’t necessarily mean that Obama’s performance measured up to the high initial expectations that the international community had of him.

In 2010, the Obama administration signed a New START (Strategic Arms Reduction Treaty) deal with Russia to limit the number of deployed strategic nuclear warheads in the two countries to 1,550.

As Washington’s relationship with Moscow has soured because of Russia’s involvement in the Ukraine crisis, however, there is no prospect for a further reduction in the two countries' nuclear arsenals.

The Obama administration adopted what is called a “strategic patience” strategy in dealing with North Korea’s nuclear arms program. The strategy means the United States will not agree to any negotiation with Pyongyang until it takes specific steps toward denuclearization.

But North Korea has conducted four nuclear tests in defiance of the Obama administration’s warnings.

Obama also carefully weighed the idea of making a declaration of “no first use,” or a U.S. pledge not to use nuclear weapons unless first attacked with nuclear weapons. It is a great shame that Obama didn’t act on it.

INHUMANE NATURE OF NUCLEAR ARMS

Last month, Trump posted a tweet saying that “the United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes.” It was seen as a reaction to Russian President Vladimir Putin’s comment about promoting Russia's development and deployment of nuclear missiles.

During his presidential campaign, Trump refused to rule out the possibility of using nuclear weapons against the Islamic State, the Muslim extremist group.

In an interview around the same time, he even suggested he could support moves by Japan and South Korea to arm themselves with nuclear weapons for their own defense.

Trump’s real intentions concerning the issue, however, are unclear as he later denied giving his support to the idea.

These remarks by Trump, who has adopted the slogan of “America first,” seem to indicate the incoming U.S. president has a worrisome inclination to put great importance on nuclear arms as the core of U.S. military power.

The biggest worry is Trump’s harsh criticism of the nuclear agreement with Iran, which he called “the worst deal ever negotiated.” He has even signaled that he may overturn the pact.

If he does that, it would have an immeasurably harmful impact on the Middle East.

In recent years, the international community has begun embracing the notion that nuclear weapons must be eliminated because they are catastrophically inhumane.

The mayors of both Hiroshima and Nagasaki have called on Trump to visit their cities, which were both devastated by atomic bombings. They want the new American leader to recognize the inhumane nature of nuclear arms.

It is vital to strengthen international pressure on the Trump administration to share this recognition.

Last month, the United Nations made a formal decision to start international negotiations for a treaty to ban nuclear arms. The proposal was adopted in a U.N. General Assembly session, with 113 countries voting for it.

The first round of talks will be held in March. But the United States, which has been strongly opposed to such a treaty, will not take part in the negotiations. Nor will other nuclear powers, including Russia and France.

JAPAN SHOULD SERVE AS A BRIDGE

Japan, which is protected by the U.S. nuclear umbrella, also expressed its objection to the start of the negotiations. But Foreign Minister Fumio Kishida has signaled Japan’s intention to be present at conferences to negotiate the treaty.

The envisioned treaty would be a big step forward toward the elimination of nuclear arms. But this undertaking should not lead to a wider rift between the nuclear powers and the rest of the world.

As the only country to have suffered the devastation of nuclear strikes, Japan, a major ally of the United States, has cast itself as a potential mediator between the two camps. Now it is time for Japan to play this very role.

Under the Japanese government’s national security policy, the U.S. nuclear arsenal is seen as the key deterrent against the threat posed by North Korea and China.

Tokyo has expressed concerns that the proposed nuclear ban would be inconsistent with this policy.

But there can be no real progress toward the elimination of nuclear weapons unless the world discards the notion that a nation can only ensure its security by maintaining nuclear deterrence.

In particular, countries that are dependent on the U.S. nuclear umbrella like Japan need to make serious efforts to help the world consign this long-established theory to the rubbish bin.

The start of the negotiations for a nuclear ban offers a great opportunity to think about this imperative.

Japan should work with other countries protected by the U.S. nuclear umbrella, such as Australia, Germany and Canada, to explore ways to produce a treaty that is acceptable to them.

One idea worth serious consideration is the establishment of a period in which these countries will gradually reduce their dependence on nuclear deterrence provided by the United States.

If their non-nuclear allies start pursuing a path toward a ban on nuclear arms, the United States and other nuclear powers may begin to consider radical changes in their own nuclear arms policies.

What Japan is expected to do is to take actions that bring about a paradigm shift in the situation concerning this vital cause.

--The Asahi Shimbun, Jan. 6