"Has North Korea Invaded any Country?" Some people say the answer is a self-evident Yes, because we all know that North Korea invaded South Korea and provoked the Korean War.
But is this answer totally satisfactory to debunk all there is to debunk? Probably Not.
First, there is a technical difference in that the Korean War was not a normal war in which one independent country invades another independent country but it was exactly like North Vietnam attacking South Vietnam for purposes of unifying their country. Now that Vietnam is one country, if Vietnamese people say that they have never invaded another country, I doubt we will be upset and protest, "Not true, you once invaded South Vietnam and conquered it." No one will be that silly. "Vietnam never invaded any country" will be considered basically true despite the fierce fightings and tragic deaths during the Vietnam War. Because there is a fundamental moral difference between an invasion by a foreign country for exploitation and a war of defense against such foreign powers.
Second, the history of the Korean War is far more complicated than meets the eye. There is even some strong historical indication that the US not only knew and anticipated the oncoming "surprise" attack in advance of the actual attack of North Korean army on June 25, 1950, but tried to induce, in various ways, North Korea's major expansion of the then-ongoing scattered fightings. (It is not known precisely why the US wanted North Korea to launch a major attack on the South but one theory is that the US wanted to ultimately draw China into a major military conflict with the US in order to "recover" China, which was just lost to the communists.)
Third, perhaps most critically, just because North Korea was the "invader" in the Korean War doesn't justify punishing North Korea for all things it does, including its monumental effort to survive. There could have been a peace treaty to bring a real closure to that bloody war in 1953. But what have we done? We refused to enter into any kind of negotiation for peace treaty and, instead, manipulated the then tragic situation to further oppress North Korea, which left them pretty much of no option, except to focus their entire national effort to a single goal of survival in the face of the huge obstacle set up by the mightiest military power.
The most dangerous people are those who know nothing but who think they know everything. To begin to understand the full context of the North Korean situation, you have to understand the history of Korea struggling to remain independent since the turn of the century circa 1905 through the Korean War and beyond. Good place to start is to read some books: The Hidden History of the Korean War, by I.F. Stone; and The Korean War: A History, by Bruce Cumings.