(CNN)If history is any guide, provocative actions from North Korea can be expected around the time of US elections, a new study says.
First on CNN: North Korea may be planning October Surprise, study says
Over the past 60 years, North Korea's leaders have attempted to incite tensions around the time of American elections -- especially in recent years, the study by the Center for Strategic and International Studies says.
For example, North Korea conducted a missile test and then a nuclear test shortly after President Barack Obama was elected.
"Doing a major test would be a way of trying to intimidate the incoming president," said Victor Cha, one of the study's authors. "North Korea chooses particular windows that they know will gain maxmum attention from the world, and the US in particular."
"It could be a sixth nuclear test, it could be launching of their rocket which put a satellite in orbit," Cha added.
The study is scheduled to be published this week on the CSIS website Beyond Parallel.
But some analysts see a shift in North Korea's provocations, from symbolic actions to concrete military tests, since Kim Jong Un took power after his father's death in 2011. These analysts see a decrease in deadly provocations that are primarily symbolic, such as the 2010 shelling of the disputed South Korean island Yeonpyeong, or the 2010 sinking of the South Korean warship Cheonan with a torpedo.
Only one has occurred recently -- the placing of land mines in the demilitarized zone, which injured two South Korean soldiers last year.
"Nothing as aggressive as we saw under his father," said Ken Gause, who analyzes North Korea's leaders for CNA Corp. "Kim Jong Un, with the exception of the August crisis of last year, he has pretty much restricted his provocations to missile tests, nuclear tests, and cyber attacks."
The past few years have seen an exponential jump in the number of North Korean weapons development tests, according to statistics from 38North, including 15 missile tests in 2016 alone.
Any provocations carry an increased risk of escalation these days, analysts say, for two reasons.
First, the South Korean government after 2010 made it easier for military commanders to respond to a provocation without waiting for politicians to consider a response.
"They are more likely to retaliate earlier than in the past; they are also more likely to respond exponentially," said former CIA analyst Bruce Klingner, now with The Heritage Foundation.
And second, Klingner said, the North's growing nuclear capability could give North Korean leaders a sense of impunity.
"They may feel more emboldened conducting not only provocations, but actual attacks," he said, "feeling that they have immunity from any kind of US response, because North Korea has a nuclear deterrent to the US nuclear umbrella."
North Korea is one of the most difficult national security challenges the next president will face, according to CIA director John Brennan.
Asked to identify America's biggest risk across the globe, he told CNN's Erin Burnett last week: "Kim Jong Un's nuclear arsenal missile capability. Not just to threaten his neighbors, but also to have intercontinental capability. That's something that the new team and the current team is looking at very, very closely and will need to be able to address."
But, national security analysts say, the US appears to have little leverage to stop the country's nuclear program from racing ahead.
"I don't think we can solve it diplomatically, that much is clear. Every administration in the last 20 years has tried a diplomatic approach, and the North Koreans have blown through every one," said CSIS's Michael Green, who himself handled such efforts when he was director for Asian affairs at the National Security Council.
"What the US can do, with allies and partners -- and hopefully China -- is constrict North Korea's access to technology, to money, slow down their nuclear program, and start setting the stage for negotiations," he said.