A US nuclear submarine armed with guided missiles has made a port call in South Korea, while Pyongyang is reportedly holding massive long-range artillery drills amid muscle-flexing in the region and rising tensions between Washington and North Korea. The USS Michigan nuclear submarine arrived in South Korea on Tuesday "during a regularly scheduled deployment to the Western Pacific," according to a statement issued by the US Pacific Fleet. The submarine is one of the four Ohio-class nuclear vessels, one of the largest in the world "measuring more than 560 feet long and weighing more than 18,000 tons when submerged." The US military praises the sub as a weapon to "provide the Navy with unprecedented strike and special operation mission capabilities." The move comes at a tense time in relations between Washington and Seoul on one side and North Korea on the other. On Tuesday, Pyongyang celebrates the 85th anniversary of the foundation of its Korean People's Army. The jubilee was marked by