A South Korean newspaper is reporting that North Korean troops are scurrying around the site where it tested a nuclear bomb on February 12, its third ever. All signs point to a fourth, and the timing couldn't be worse. "There are recent active movements of manpower and vehicles at the southern tunnel at Punggye-ri," says the newspaper JoongAng Ilbo. "We are monitoring because the situation is similar to behavior seen prior to the third nuclear test." Meanwhile, South Korean officials say that they expect North Korea to test another missile this week, probably on Wednesday.

Well, this isn't good. The tense situation between the North Korea and, well, pretty much everyone on Earth has been escalating in the weeks since that third test and has become increasingly severe since last week, when supreme leader Kim Jong Un's top brass promised a "merciless" attack on the United States. South Korea is more or less preparing for a war, while the United States has threatened a swift and decisive response it there is an attack. Even though President Obama's senior advisor Dan Pfeiffer played down the threat of violence — he said this is just "a pattern of behavior we've seen from the North Koreans many times — the U.S. military's been drawing up a plan in case it does. Accordingly, the U.S. commander in South Korea canceled a pre-planned trip to Washington, just in case something does go down this week.

This all puts the U.S. in a really awkward position. On one hand, it needs to be prepared for the worst, hence the planning. However, it doesn't want to overdo it, since that might scare the North Koreans into a launching a preemptive attack. At the same time, the U.S. is working hard to keep South Korea calm, because if they get too anxious and launch their own attack or even appear to be preparing one, North Korea could try to hit them first. That would be bad. On the other hand, the government really doesn't want to scare the bejesus out American citizens.

But really, the main challenge goal at this point is not to start war. It's not going to be easy, especially with these worrisome new reports. Gary Samore, Obama's former director of mass destruction and arms negotiation, summed it up well in an interview with The New York Times on Sunday. Flagging the threat of an attack on Seoul, Samore said, "Everyone is aware there are not big margins for error here."