Paramilitary force organizations, under the Central Government, are the protective services that have been constituted to maintain internal security, and support Defence services of the country, which are responsible for guarding our national boundaries from external aggression. The Paramilitary Forces of India (PMF), that has over a million personnel active in its service, are the agencies of the Ministry of Defence or the Ministry of Home Affairs which act as armed forces auxiliaries. Considered as a part of the Indian Armed Forces, they provide additional support to the defence forces in guarding the national frontiers, help the Law Enforcement Agencies and the Indian Armed Forces in their operations. PMF is regarded as the world's second largest paramilitary organization (second only to the Chinese Peoples Armed Forces) and its head officers and other senior officers being members of Indian Police Service (IPS). PMF helps the army, the navy, the Air force and the state police whenever required. The organizations that serve as the paramilitary forces of India are : Central Reserve Police Force (CRPF), Border Security Force (BSF), Indo-Tibetan Border Police (ITBP), Central Industrial Security Force (CISF), National Security Guard (NSG), Railway Protection force (RPF), Special Frontier Force (SFF), Assam Rifles, Vigilance Organisations, Fire Services, State Police Forces and Coast Guards. Each of these units play a well-defined role besides coming to the nation's rescue at times of national calamities and emergencies. All the branches of PMF excluding the Indian Coast Guard are under the Ministry of Home Affairs. The largest force of the PMF is the Central Reserve Police Force (CRPF) which assists the Indian Police in maintaining law and order. The CRPF, BSF and ITBP together constitute the Central Police Organizations (CPO). How to Join in Para Military Forces One can enter any service of the Paramilitary Forces of India (PMF) after completing their Class X, XII or Graduation. Women are also allowed to enter the paramilitary forces services. Graduates in any stream, who are 20- 25 years of age may apply for recruitment to the posts of sub-inspectors in BSF, CISF, CRPF, ITBP and SSB. Female candidates are eligible for recruitment to CISF and CRPF only. Physically handicapped candidates are not eligible for these posts.