In the 1976 psychological drama "Taxi Driver," Robert De Niro plays a socially outcast cab driver. In a real-life drama today, North Korea's Kim Jong Un is an internationally isolated world leader. In both roles, these characters communicate messages delivered with a sense of bravado, taunting a non-existing threat.

In an iconic scene in the movie, De Niro, alone in his room, is on an adrenaline high precipitated by insomnia. Looking in the mirror, he challenges no one with, "You talkin' to me? Well, I'm the only one here! You talkin' to me?"

In North Korea, Kim Jong Un is on an adrenaline high due to the success of his country's third nuclear test -- this on a device purportedly smaller and lighter than the others and, thus, capable of placement into a long-range missile.

Issuing his challenge, the well-fed leader -- a giant compared to his diminutive, underfed countrymen -- warns he will take further steps if the United States maintains its "hostile approach" toward North Korea. Trying to create the illusion of a U.S. threat where none exists, Kim taunts an America perceived to be the lion from the Wizard of Oz -- i.e., lacking the courage of its convictions.

Pyongyang knows there is nothing to fear from U.S. foreign policy toward the North -- whether under a Republican or Democratic president, whether the talk is tough or not, whether sanctions were increased or lifted -- for such policy has always failed to influence its conduct away from aggression and nuclear armament.

Years of U.S. and South Korean appeasement have only served to encourage it. As a result, for years, the United States and South Korea have repeatedly been victimized by unprovoked aggression. To this day, a U.S. warship remains in North Korean hands as a continuing reminder of it.

Past U.N. efforts to ratchet sanctions up on the North have been blocked by Pyongyang's big brother -- China -- claiming it seeks to keep the peninsula "stable."

But such protection by China of the North's misdeeds only creates instability. As the North's prime supplier of food and fuel, China should have had leverage to dissuade it from conducting its most recent nuclear test. It did not.

Thus, questions now arise over China's ability to exercise control over the rogue state. Another big brother now flexes its muscle, apparently exerting greater influence over the North.

In his Feb. 12 State of the Union address, U.S. President Barack Obama said: "The regime in North Korea must know they will only achieve security and prosperity by meeting their international obligations ... Likewise, the leaders of Iran must recognize that now is the time for a diplomatic solution, because a coalition stands united in demanding that they meet their obligations and we will do what is necessary to prevent them from getting a nuclear weapon."

As to North Korea, it should not come as a shock to Obama but, in achieving "security and prosperity," Pyongyang's leadership has zero interest in "meeting their international obligations."

Thinking the leadership expends any energy worrying about the "security and prosperity" of people is wishful. One need only consider treatment of their own people -- the millions of North Koreans who have died of starvation under three generations of the Kim family's rule; or the generational height and weight decline of the average North Korean army recruit, caused by famines, relative to corresponding size increases of their South Korean counterparts, caused by better nutrition; or that North Korea hosts the largest gulag in the world, including some whose only crime is being related to an ancestor who committed a crime against the state a generation earlier.

Its unconcern is reflected by a famine policy that simply waits until enough citizens die to stabilize the food shortage.

As China's influence over Pyongyang wanes, that of another big brother, also mentioned by Obama, waxes. The North's nuclear program has long been of keen interest to Iran. One cannot forget it was North Korean assistance, provided at Iran's direction and with its funding, that led to the effort to secretly build a nuclear facility in Syria. That effort ended in 2007 in an Israeli attack.

Iran is determined to get nukes either on its own or via a proxy. And Pyongyang, given the appropriate financial incentive, is a more-than-willing proxy. Meanwhile, Tehran dismisses Obama's threat to stop it from acquiring such weapons as a cowardly lion's bravado.

The real threat the North poses to the United States is its willingness, for the right financial incentive, to sell nuclear technology. It is highly unlikely Pyongyang itself would ever use it for fear of U.S. retaliation, endangering Kim Jong Un's most valuable asset -- his own life.

But selling it to a country like Iran, undeterred by U.S. retaliation, would result in its being used to trigger the world chaos mandated by Iran's religious prophecy.

Yet another event can now be added to the endless list of "provocative acts" undertaken by the North as it continues its journey for nuclear weapons. As a gambling man would bet on Iranians using North Korean nuclear technology to create world chaos leading to its Islamic eschatology, Kim Jong Un should be advised any such act by Iran will result in North Korea's "most valuable asset" being placed in America's retaliatory cross hairs. Doing so relieves Kim of having to query, "You talkin' to me?"

(James G. Zumwalt is a retired Marine infantry lieutenant colonel who served in the Vietnam war, the U.S. invasion of Panama and the first Gulf war. He is the author of "Bare Feet, Iron Will--Stories from the Other Side of Vietnam's Battlefields," "Living the Juche Lie: North Korea's Kim Dynasty" and "Doomsday: Iran--The Clock is Ticking." He frequently writes on foreign policy and defense issues.)

(United Press International's "Outside View" commentaries are written by outside contributors who specialize in a variety of important issues. The views expressed do not necessarily reflect those of United Press International. In the interests of creating an open forum, original submissions are invited.)