

OK, it’s not “all” about the tightly closed Stalinist regime’s 30-year-old supreme leader and noted Dennis Rodman pal. There are allies like South Korea to reassure, global markets to calm, and rivals and foes to impress.

But President Barack Obama’s muscular response to North Korea’s escalating saber-rattling—a response that has included ordering nuclear-capable bomber flights over the Korean Peninsula, dispatching U.S. warships to the region and beefing up missile defense systems—owes a lot to the fact that it’s Kim’s first major confrontation with America and its allies.

Kim took over in December 2011 after the death of his father, Kim Jong Il, who regularly defied the international community. The elder Kim tested nuclear weapons, test-fired missiles, and in a pair of 2010 incidents shelled a South Korean island and allegedly sank a South Korean navy ship. His regime repeatedly promised to turn South Korea's capital, Seoul, into a “lake of fire.”

His people starved. He parked many into prison camps regularly denounced by human rights groups as among the most brutal in the world. He allegedly shared nuclear and missile know-how with countries like Iran and Syria. How could the younger Kim be worse?

“There is some concern that maybe, unlike his father, this guy doesn’t know where the edge is—he keeps pushing, and doesn’t know where the edge is,” Victor Cha, the top Asia hand on President George W. Bush’s National Security Council from 2004-2007, told Yahoo News.

Obama’s response sends a message, Cha explained: “If you don’t know where the red line is, we’re going to draw it for you.”

Peter Brookes, who served as Bush’s deputy assistant secretary of defense for Asian and Pacific affairs, called the standoff uncharted territory.

“This is the first serious crisis we’ve had with this new leader and this regime,” Brookes said.

Kim "doesn’t want to nuke New York,” Brookes added. “But there is a high likelihood that he’ll have to do something based on all of the threats that he’s made, because if you make threats and you don’t fulfill them then they lose their meaning, they lose their leverage.”

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The U.S. approach naturally has other goals.

At the White House briefing, press secretary Jay Carney repeatedly said the U.S. response is meant to “reduce pressure on Seoul to take unilateral action.” Carney also denied that Washington's actions risked escalating the crisis. "Not at all," he said.

American military officials in the region worry that South Korea could miscalculate and cause "some kind of escalation where we can't pull back the ROKs (South Koreans), and it becomes a wider crisis," a congressional aide familiar with policy toward the region told Yahoo News, referring to South Korea's official name, Republic of Korea. The aide requested anonymity in order to speak candidly.

Gen. James Thurman, the top U.S. commander in South Korea, told ABC News in an exclusive interview that he has never seen the situation tenser in his two years on the job.

Jim Walsh, an international security expert who teaches at the Massachusetts Institute of Technology’s Security Studies Program, recalled a briefing with uniformed American officers some time ago in which one explained that the purpose of U.S. forces on the Korean Peninsula was “to deter North Korea and restrain South Korea.”

Some of South Korea’s English-language papers have been playing up the importance of hand-in-glove cooperation with Washington.

“So, sure, there’s an element of telling North Korea ‘be careful what you wish for,’ but I think the primary audience was our allies, and the American audience,” Walsh said of South Korea's message.

The show of American military might also aims "to show allies that we’re not going to sit back and allow them (North Korea) to do this sort of stuff," said Cha.

That "stuff" really began in December 2012 when North Korea tested a long-range rocket. That provocative act was followed quickly in February with a nuclear test. Both steps drew condemnation from the international community, and the U.N. Security Council tightened already stringent sanctions on Pyongyang, which countered with a stream of escalating menace.

The regime seized international headlines with threats to carry out nuclear strikes against the United States and South Korea, repudiated the armistice that halted—but did not technically end—the Korean War, and vowed to reopen a nuclear reactor thought to be able to produce enough plutonium to make one atomic bomb per year.

Secretary of State John Kerry is due to visit South Korea, China and Japan starting April 12. It will be his first visit to Asia since taking office, and North Korea will surely dominate the agenda.

"I don't think the administration has any other choice" than take a hard line, the congressional aide said. "They can't put more carrots down on the table or they'll look incredibly weak and naive—they know that."

A major challenge for U.S. policymakers is that North Korea—sometimes dubbed "the hermit kingdom"—is tightly closed to outsiders, the analysts said.

"Fundamentally, we don’t know what’s going on," said Walsh. "We have to continually remind ourselves that this is the most opaque country in the world."

And what role is Kim playing in all this? Unclear, Cha said.

"We don't know what his relationship is to the military. We don't know what his relationship is to the party," Cha said, referring to the totalitarian state's Communist bureaucracy.

Because of that uncertainty, American policymakers "must be challenged by not having a good feel for Kim Jong Un," Brookes said.

"What you really have to do is discern intent," Brookes said. "I’m worried that he might be anxious to prove his mettle."