Yet despite what you say, they have launched attacks on many, many occasions in the past. Here's a selection:
- May & June 1996: North Korean vessels twice cross the Northern Limit Line and have a several-hour standoff with the South Korean navy.
- April 1997: Five North Korean soldiers cross the Demilitarized Zone in Cheolwon, Gangwon-do, and fire on South Korean positions.
- June 1997: Three North Korean vessels cross the Northern Limit Line and attack South Korean vessels two miles (3 km) south of the line. On land, fourteen North Korean soldiers cross 70 m south of the center of the DMZ, leading to a 23-minute exchange of fire.
- June 29, 2002: Renewed naval clashed near the Northern Limit Line lead to the deaths of four South Korean sailors and the sinking of a South Korean vessel. The number of North Koreans killed is unknown.
- March 26, 2010: A South Korean naval vessel was allegedly sunk by a North Korean torpedo near Baengnyeong Island in the Yellow Sea. A rescue operation recovered 58 survivors but 46 sailors were killed. On May 20, 2010, a South Korean led international investigation group concluded that the sinking of the warship was in fact the result of a North Korean torpedo attack.North Korea denied involvement.
- November 23, 2010: NK fired artillery at South Korea's Greater Yeonpyeong island in the Yellow Sea and South Korea returned fire. Two South Korean marines and two South Korean civilians were killed, six were seriously wounded, and ten were treated for minor injuries.
NK's view is that it's ok for them to kill a few SK citizens every now and then without retaliation, whenever the NK leader needs to make a new propaganda video.
When a country shows on their own national TV its leader poring over a map of the US labelled "target', and this nation then launches a missile of unknown capability and unknown destination without warning, there is bound to be a high level of risk.
It's the UN not NATO. And since the war has never been undeclared, either side could choose to attack any time they like.