North Korean leader Kim Jong Un gives field guidance at the newly built Wisong Scientists Residential District in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang, Oct. 14, 2014. (Reuters/KCNA)

Despite some signs of a fresh openness in Pyongyang after the return of the absent North Korean leader Kim Jong Un, a recently published memoir is bringing all of the country's indignant rhetoric back at full force.

First, a tersely worded article published last week by North Korean state newspaper Rodong Sinmun hit out in response to what it says was "the first time that a U.S. war boss openly declared that it would use nuclear weapons against the DPRK."

That article was followed on Monday by a commentary from KCNA, the state news agency, which wrote that North Korea will "further bolster up its nuclear deterrence for self-defense both in quality and quantity" until they "completely foil the U.S. hostile policy toward the DPRK."

The spark for North Korea's ire is "Worthy Fights," a memoir by the former defense secretary and CIA director Leon Panetta. It's a book that has already caused some controversy in the United States due to its portrayal of President Obama's foreign policy. However, on the Korean peninsula, it got attention for another reason: Panetta appeared to reveal the U.S.'s plans for nuclear strikes against North Korea should the South be invaded.

The passage in question recounts a 2011 briefing given to Panetta by Gen. Walter L. “Skip” Sharp, the commander of U.S. forces in South Korea. During that briefing, Panetta recalled that he was advised that:

"If North Korea moved across the border, our war plans called for the senior American general on the peninsula to take command of all U.S. and South Korean forces and defend South Korea -- including by the use of nuclear weapons, if necessary."

Panetta, then secretary of defense, goes on to say that he left the meeting with "the powerful sense that war in that region was neither hypothetical nor remote but ever-present and imminent.”

The comments received a large amount of attention in the South Korean media when they were first revealed earlier this month, with one South Korean paper writing that Panetta had revealed the "nuke plan for South Korea." Some observers were less shocked, however – while the United States withdrew its nuclear weapons from South Korea decades ago, a U.S. "nuclear umbrella" is understood to be part of South Korea's defensive options. Panetta himself acknowledged this in a 2011 op-ed for a South Korean newspaper, Chosun Ilbo.

In an article for Foreign Policy, Jeffrey Lewis of the James Martin Center for Nonproliferation Studies argued that nuclear weapons had been tacitly acknowledged as part of a defense plan for South Korea, but their importance was more a symbolic reassurance than a practical threat. "Were the United States to engage in a full-scale conflict with North Korea, we simply would not use nuclear weapons for the same reasons we did not use them in Iraq," Lewis wrote. "We don't need nuclear weapons to defeat North Korea and there is no justification for victimizing the North Korean populace a second time."

Nuclear deterrence has its obvious support in South Korea, where some polls show strong support for a home-grown nuclear program, too. However, it obviously has its effects in North Korea, too, where the country justifies a weak yet worrying (and potentially self-sufficient) nuclear program by claiming that it is its only option. As the Rodong Sinmun puts it, "Maniacs brandishing nuclear sticks should be beaten by nuclear sword."