UN investigators recently concluded that North Korea had illegally converted Chinese lumber transports into TELs (Transporter Erector Launchers) for its KN-08 ballistic missiles. It was only in the last year that TELs carrying the KN-08 (also known as the Taepodong-2) were seen in public. The KN-08 is a large missile with a range of over 4,000 kilometers and required a very large TEL to carry it. The KN-08 and its TEL first appeared in a North Korean military parade. There for the world to see was a 16 wheel TEL carrying what appeared to be a three stage ballistic missile. Both the TEL and the missile had not been seen like this before. What was odd about the KN-08 was that it had only been tested once (in 2006) and that failed. North Korea has never been known to deploy a long-range missile that had not been successfully tested. Some thought KN-08 was a fake, just something to make the cold, hungry, and broke North Koreans feel better about themselves. Markings on the TEL identified it as “Hwasong-13 Self-Propelled Launcher.” There are two other North Korean Hwasong missiles, both of them short (up to 500 kilometers) range liquid fuel rockets. These two were called Hwasong-5 and Hwasong-6. Defectors from North Korea indicate that the official name for all North Korean ballistic missiles is Hawsong and that indicates that a missile named Hwasong-13 could be the latest one.
The most interesting aspect of all this was the TEL, which is a large truck specially built to carry, then erect and survive the launch of a ballistic missile. The North Korean TEL was unlike any seen before up there but the cab was similar to a Chinese heavy transporter. It was initially believed that North Korea bought these heavy trucks and then modified them into TELs. This is what Iran did for a long time, until sanctions officials ordered heavy truck manufacturers to stop selling Iran the big vehicles that could be converted to TELs by the buyer. It eventually discovered that the North Korean TEL was based on a Chinese vehicle exported to North Korea as a lumber transporter (a legitimate use for trucks like this).
Large trucks modified to be TELs are often not real TELs. There are a lot of manufacturers out there who build huge (12-20 wheel) trucks, and these are often used to carry military equipment (like 60 ton tanks). A 12-50 ton ballistic missile is no problem but installing the hydraulic gear and controls to erect the missile to a vertical position is tricky. Even more difficult is hardening the rear of the vehicle to minimize the damage from the rocket exhaust. This last bit can be dropped if you only expect to use these TELs once for a live fire. The 16 wheel North Korea TEL appears to be one of those "use once and abandon the trailer" models. UN investigators found that North Korea had bought six Chinese WS51200 transporters two years ago, for $817,000 each. China believed it would be too difficult to convert these into TELs but the North Koreans proved them wrong. The Chinese cooperated with the UN investigation and pointed out that the WS51200 sale contract specifically prohibited use of the vehicles for military purposes.
It is believed that the North Korean TELs and their cargoes are being moved around to build North Korean morale and to mess with foreign intelligence agencies. North Korea has been observed carrying on like this before but never on such a large scale. The North Koreans assume that the U.S. and South Korea know where the fixed missile launching sites are and plan to hit them with smart bombs in the early hours of a war. But the mobile TELs can avoid detection for a while, often long enough to launch their missiles at key targets (air bases, headquarters, etc.).