The weather and the geography of the Korean peninsula made it a very difficult place to conduct the Korean War. Some believe it to be the worst place on earth for a war. Neither the weather nor the geography has changed since 1950-1953.
If hostilities erupt again and develop into Korean War 2, the army of North Korea will invade South Korea within hours, creating millions of refugees and pushing the US forces and the South Korean army southward. Then Donald Trump’s options will be limited to bombing civilians in North Korea and/or bombing North Korean troops in South Korea, killing adjacent friendly troops and civilians. Essentially destroying South Korea to save it as we did in Vietnam.
During the first Korean War, General Douglas MacArthur, the US commander, wanted to nuke the 880 mile long border between China and North Korea to create a radioactive zone to prevent Chinese troops from entering the war. President Truman wisely said no. Since Trump likes walls, he might approve of the idea. China would object, and China too is a nuclear power.