Saudi Arabia has commenced a massive military drill in which 20 nations are participating. The move comes amid ongoing deadly conflicts in the Middle East. More than 2,500 warplanes, 20,000 tanks and 450 helicopters will be part of the exercise. Riyadh has billed the manoeuvre as "the largest and most important" drill ever staged in the region. Up to 350,000 troops from various Gulf nations, and other allies such as Pakistan, Jordan, Chad and Sudan will take part in the drill, the Saudi Press Agency said. The exercises would involve ground, naval and air forces personnel.