Holy Moses! A mass exodus of North Korea workers from Russia!

The Independent is talking up the return of some twenty thousand North Korean workers in the Russian Far East back to North Korea as a sign that the North may be preparing for war:

A mass exodus of North Korean workers from the Far East of Russia is under way, according to reports coming out of the region. As the two Koreas edged towards the brink of war this week, it appears that the workers in Russia have been called back to aid potential military operations.

Vladnews agency, based in Vladivostok, reported that North Korean workers had left the town of Nakhodka en masse shortly after the escalation of tension on the Korean peninsula earlier this week. "Traders have left the kiosks and markets, workers have abandoned building sites, and North Korean secret service employees working in the region have joined them and left," the agency reported.

The workers are largely employed in construction, they are strictly controlled by Nork handlers who keep a close eye on all their activities, and most of their money is believed to go back to North Korea through government accounts.

Now what this all means is anyone's guess. I'd start by asking, Is this rare? I recall back in the mid-1990s, when the peninsula seemed on the brink of war over North Korea's nuclear program, several Western media outlets reported that things were so tense in South Korea that the authorities were conducting air raid drills. Yep, the turista journalistas who knew little about South Korea except that it was below North Korea were reporting that monthly air raid drills were a new response to all the tension. It would not be outside the realm of possibility that a routine or coincidental return of workers is being seen as a sign of something it's not.

But what if it is a deliberate response to the North-engineered crisis, Does this mean the DPRK military needs all the bodies it can get? I would think construction workers who can't even be trusted not to defect would make lousy soldiers (also because they lack recent military training). Surely a donnybrook in the Yellow Sea would warrant the deployment of actual soldiers.

If there is a connection with the Yellow Sea crisis, Could it be that Pyongyang fears these expat workers will flee if chaos erupts back in the Homeland? To me, this feels like a better explanation. Maybe things back inside the DPRK are shakier than we realize (which could be the reason for the Yŏnpyŏng-do shelling in the first place). If I were in charge of North Korea and I thought a war was going to break out, I'd want twenty thousand potential guerrilla fighters to stay outside the country until they're needed. But that's me. (Actually, I'd sign over the DPRK into some kind of confederation, and then I'd run for president.)

Another question to ask is, Is North Korea just messing with our heads? Though they do lose some hard currency by bringing the construction workers home, there may be some value in making the outside world think they're bringing back the workers for some military purpose. And as an added fringe benefit, it forces people like me to waste mental energy trying to figure out what they're up to.

UPDATE:
Joshua Stanton, citing this link from NK Economy Watch, suggests there may be something to my idea that the North Korean workers in Russia might take off if there is chaos on the Peninsula.

North Korean workers in Vladivostok during happier (and warmer) times. 
[source]