So the North Koreans shelled a South Korean island, for no apparent reason and are declaring this to be a great victory. As there is no actual response from the South, I guess it is. The usual reason for the irregular fits of childlike behavior from the Norks is that they're out of food and/or fuel. The multi-nation conference that inevitably follows such an outrage usually ends with the Norks promising not to do whatever it was again without provocation, and everybody else giving them large quantities of food and fuel.
In the somewhat further distant past, having your neighbor lob artillery shells over your border was the clarion call to call up your reserves and break out the plans for rectification of the border. I distinctly remember the ROK marines in Viet-Nam as being among the baddest bears in the woods there to the point that the Cong went out of their way to avoid them.
The current leadership in South Korea has announced official outrage and has promised quick and harsh retribution.
If the North does this again.
The current leadership in the South is evidently not an ex-ROK marine.