US and South Korean troops have begun large-scale spring exercises to counter ongoing tensions with North Korea. The annual training exercise, codenamed Freedom Shield, started as planned, the Ministry of National Defence in Seoul said on Monday. The 11-day exercise includes computer simulations and drills in the field. It was initially unclear how many soldiers would be involved. According to South Korea, defence against nuclear threats from North Korea will be a core element of the training exercise. The US and North Korea’s neighbours South Korea and Japan see themselves directly threatened…