Today, we have North Korea's Kim Jong-un.

The history is similar. Bill Clinton, George W. Bush and Barack Obama all tried combinations of talks, partial sanctions, aid and subsidies. Every time they tried to encourage or cajole the various members of the Kim dynasty to stop going down the path of obtaining nuclear weapons and the wherewithal to deliver them intercontinentally, the Kims just ignored them and pressed on.

This week, the new South Korean President tried the same thing, saying he wanted to open a channel of dialogue with North Korea while maintaining sanctions. North Korea's response was to launch a missile that travelled 700 kilometres before dropping into the Sea of Japan, and to engage in worldwide cyber attacks.

Clinton and Bush's efforts culminated in North Korea testing an atomic bomb in 2006. United Nations sanctions were imposed in 2006, but the Obama administration failed to use all of its financial and diplomatic power to enforce the sanctions to bring the regime to its knees. This was through fear of angering China and because South Korea thought the North could be persuaded to open up to the outside world and end its nuclear program.

It is fine to be persuasive, compassionate and generous within the boundaries of a democracy, but this is a waste of precious time – and it is precious – when dealing with people like Kim Jong-un.

The North Korean regime is determined to build a nuclear bomb small enough and a missile powerful enough to threaten continental United States and, for that matter, Australia. No amount of persuasion or attempts at dialogue will dissuade it.

It is highly dangerous to try. If Clinton, Bush and Obama failed, what chance has Trump, who makes Bush look like a foreign-affairs sophisticate and statesman?

The only thing that will stop Kim Jong-un perfecting the multibillion-dollar nuclear program begun by his grand-father, Kim Il-sung, and continued by his father, Kim Jong-il, is duress so great that it threatens his regime.

Look at the history. Clinton's 1994 "agreed framework" gave Kim Jong-il's regime fuel aid and help to build two peaceful nuclear power stations in return for a promise to give up the nuclear-weapons program. It was worse than folly. It probably helped the North's nuclear-weapons technology.

Bush ended the framework when he discovered North Korea was cheating. Then he stupidly entered his own agreement to ease sanctions, remove North Korea from the state-sanctioned terrorism list and, worse, allow North Korea to use the dollar system.

Shortly after Obama came to office, his "reaching out" was met with the first long-range missile test and then the testing of a nuclear device. In 2012, Obama entered the aid-for-nuclear-freeze leap day agreement. Six weeks later, North Korea tested a long-range missile.

Meanwhile, South Korea engaged in several economic and food-aid arrangements, hoping to lure the North into the global economic system and to liberalise the regime. Again, worse than foolish. The South handed hard currency to the North, which it used for the weapons and missile programs and to stave off economic collapse and military rebellion.

Hitler, you must not remilitarise the Rhineland and we will ease war reparations. Hitler, leave Austria alone. Hitler, do not occupy any part of Czechoslovakia. Every time, he just ignored Britain, France and the US. Every time, he gained time to build up his weapons systems. The allies foolishly waited until Poland was invaded. By then, it was too late to avoid catastrophic war.

Trump has at least seen that he needs Chinese help. His rhetoric with China has moved from "currency manipulator" and "American job-stealer" to President Xi Jingping delivering "tremendous goodwill and friendship".

But China is unwilling to bring the North Korean regime to its knees. It will require the US to bring full duress. Yet that duress will require a great deal of subtle and intelligent use of massive financial coercion. Subtlety and intelligence are not Trump's hallmarks.

The key here is to undo Bush's deal to allow North Korea into the dollar system and to impose third-party sanctions on corporations or nations that have any dealings with the North, particularly Chinese banks. Give these banks a choice between continued dealing with the US or dealing with North Korea: they will choose the former, whatever the Chinese government urges. Profit before politics.

Tell third-world nations that now import North Korean weapons and reflag North Korean ships to stop or face expulsion from US markets.

North Korea keeps most of its currency reserves in US dollars. The US could mandate that any bank that dealt with the North would be denied access to the dollar system. US banks would be banned from dealing with North Korean-sourced dollars.

China regularly votes for sanctions in the UN but allows its state-owned corporations to ship arms and weapons technology and, importantly, the luxury goods for the elites who prop up the regime.

The US should forget the Chinese government. Rather, it should use every financial weapon at its disposal to deny the North Korean regime the wherewithal to sustain either its weapons program or, indeed, itself.

It will take time – time we may still have if no more silly appeasement arrangements are put in place.

The plus and the minus of Trump is that he enjoys chaos. That will be fine if he avoids military action and instead forcefully tells the Chinese and South Koreans that the US and its allies would prefer the chaos of a North Korean regime collapsing under the toughest financial and third-party sanctions ever seen than have a "stable" nuclear-armed North.

The big problem with Trump would be if Russia moved in to fill the Chinese vacuum. His conflict of interests might be too great to do much about it.

That aside, this is an existential threat to the democratic world and requires a response of an existential threat to the North Korean regime.

If Hitler had developed a deliverable nuclear weapon late in World War II, as he hammered the V1 and V2 doddlebugs across the English Channel, could anyone imagine him not using it?

crispinhull.com.au