South Korea to blame?

S.Korea says it test-fired in area before N.Korea firing

South Korea said it was conducting regular military drills off the west coast before North Korea started firing dozens of shells, but that its firing exercises did not aim to the North.

"We were conducting usual military drills and our test shots were aimed toward the west, not the north," a South Korean military official said.

North Korea said on Tuesday that Seoul had initiated firing of shells, prompting it to take an instant military action.

Link:
http://www.reuters.com/article/idUSTOE6AM05P20101123

Related article:

Why North Korea Attacked

North Korea's reason for going on the offensive seems to be anger over a military drill it said was "simulating an invasion of the North," according to the NYT.

The military drill, called Safeguarding The Nation, is a annual exercise involving 70,000 troops along with some American forces.

Read more: http://www.businessinsider.com/why-north-korean-attacked-2010-11#ixzz169H21LdK