OVERVIEW:  The Dong Feng 21A aka DF-21A aka CSS-5 Mod 2 battalion is a road-mobile MRBM unit, using a two stage, single DF-21A missile armed with a 500 KT nuclear warhad.  

DETAILS:

The DF-21 is likely intended for use in war-opening/escalating strikes aimed at decisively neutralizing a superior adversary’s forward forces and military infrastructure. Additinally, conventionally-armed DF-21 may be intended for use in the whole duration of a conflict for long range strikes including preemptive or suppressive strikes against major force groupings as they assemble for an operation, opportunistic strikes against fleeting high campaign-value targets, or direct/indirect fires—including possible feint attacks—in support of PLA Joint combined arms operations. 

The missile uses inertial guidance and both GPS and radar based terminal guidance 
Though the launcher itself is mobile to reduce vulnerability, an actual launch unit requires support vehicles that can cover a 300×300-meter area, making it hard to move quickly and easier to detect. Also, the launcher is not made to travel off-road and requires solid ground when firing to prevent backblast and debris damage due to the hard launch, restricting its firing locations to roads and pre-made launch pads.

Specifications:

Maximum Range:			1770 km
CEP:		 		100-300 meters
Reload time:			 12 minutes 
Reaction Time			 several minutes
Mobility:			 road mobile
Set Up Time:			 10-15 minutes

NOTES:  IOC 1996.  It was designed for deployment aboard China's SSBN, and it was decided to also develop it as a land-based missile, which was designated as the DF-21.
  

SOURCES: Administrator. (2018, September 29). DF-21 / DF-21A (CSS-5) / DF-21B medium-range road-mobile ballistic missile | China Chinese army missile systems vehicles | Chinese China army military equipment armoured UK. Defense News security global military army equipment technology industry - Army Recognition. https://www.armyrecognition.com/china_chinese_army_missile_systems_vehicles/df-21_/_df-21a_css-5_/_df-21b_medium-range_road-mobile_ballistic_missile.html ; DF-21 - China nuclear forces. (n.d.). Federation Of American Scientists – Science for a safer, more informed world. https://fas.org/nuke/guide/china/theater/df-21.htm ; O'Connor, S. (n.d.). PLA ballistic missiles. Air Power Australia. https://www.ausairpower.net/APA-PLA-Ballistic-Missiles.html#mozTocId8319