A South Korean military source says North Korea has deployed some 900 tanks over the past seven years.

The source said Wednesday that the number of the new, upgraded tanks, known as the Cheonma and the Sungoon, is more than double the number of tanks South Korea deployed from 2005 to 2012.

The source said this is the first time that the Sungoon, named after former North Korean leader Kim Jong-il’s military first policy, was found to be deployed.

The Joint Chiefs of Staff discovered that the Sungoon had been put into the field when it analyzed North Korea’s ground troops’ order of battle late last year.