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Around 50,000 former soldiers, sailors and air personnel are listed on the Regular Reserves register with an obligation to be “called back to the colours” in times of national emergency and war. It comes as Chief of the Defence Staff General Sir Nick Carter described the mission to help counter the pandemic – Operation Broadshare - as an "enduring operation” that could last six months without any leave for soldiers.

In a memo to commanders, Gen Carter highlighted a series of measures being prepared to ensure that troop formations called for the Military Assistance to the Civil Authority (MAC-A) operation remain at 80 percent combat effectiveness. Britain last called out its regular reserves in limited numbers during the Gulf War. This time, the numbers are expected to be much higher, though military planners will begin by selecting those who left recently with priority skillsets. They will support troops already deployed in field hospitals, ferrying logistics and manning distribution warehouses where food and medical supplies could become highly valued stores in the future. Some may have to undergo specialised refresher training. READ MORE: Coronavirus deaths: One in every 10 will die says, ICU doctor

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Unlike the volunteer Army Reserve, regular reservists do not train after leaving the Armed Forces and do not have a uniform at home. Instead, they are retained by name on a computer database as part of the country's strategic plan to call them out in time of national crisis. The list is categorised by skillset, rank and time served. Famously, former soldiers who could not be deployed in theatre because of their age or health formed the backbone of the Home Guard during the Second World War, tasked with protecting Britain from German invasion. The Regular Reserve was officially formed in the 1960s, and every 15 years, former soldiers are sent a letter asking them to report to a mobilisation centre to test the system. The last call-out day was 12 years ago. DON'T MISS:

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Some 50,000 former soldiers, sailors and air personnel will tackle COVID-19