The US as well as South Korea started their annual military drills called Key Resolve on 11 March 2013 despite tensions with North Korea in context with the UN sanctions vote. The annual military drills came just a few days after UN approved the new sanctions on North Korea after it carried out the nuclear test in February 2013.
The nuclear test in February 2013 was the third test of the communist country. It came after the successful launch of three-stage rocket in December 2012, which was actually the banned test of missile technology. The UN sanctions came after the underground nuclear test of North Korea on 12 February 2013. These were the fourth set of UN sanctions imposed since the first nuclear test of North Korea in 2006.
US-South Korea joint drills
The joint drills carried out by US and South Korea are called Key Resolve. These will last for two weeks and will include over 13000 troops. Apart from Key Resolve, another joint drill called Foal Eagle was on its way since the starting of March 2013.
Key Resolve is primarily a computer-simulated exercise which also involves mobilisation of over 10000 South Koreans as well as 3500 US military personnel.
Both these exercises take place annually which prompt strong reactions from North Korea.