Defence Nuclear Material Transport Operations refer to the movements of military Defence Nuclear Materials (DNM) within, to and from the United Kingdom. Defence Nuclear Material Transport Operations are also known as DNM Transportation; Defence Nuclear Material in transit; Nuclear movements; and DNM movements. The Special Escort Group of the Ministry of Defence Police, SEG (MDP), escort the nuclear materials and remain on standby during their transit. Immediate Response Forces (IRF) are embedded within the road and rail transports, and on standby with air transports.