Troops are to begin deploying in London amid growing medical staff shortages due to COVID-19 in the United Kingdom.
Around 200 armed forces personnel are being made available to hospitals across the capital, which has been the centre of the Omicron outbreak with a huge upsurge in cases.
The announcement comes after Prime Minister Boris Johnson said this week ministers hoped to "ride out" the latest wave without the need for further restrictions in England.
The Ministry of Defence said the deployment included 40 military medics and 160 general duty personnel to help fill gaps caused by absences of NHS staff unable to work because they were ill or having to self-isolate.
They will be deployed in 40 teams of five - comprising one medic and four support personnel - and will be targeted at areas where the need is greatest.
It is expected they will be "on task" for the next three weeks.
In addition, 32 military co-responders are being provided to support the South Central Ambulance Service, working alongside paramedics until the end of March.
"The men and women of our armed forces are once again stepping up to support their dedicated colleagues in the NHS as they work hand-in-hand to protect the nation from COVID-19," Defence Secretary Ben Wallace said.
"They have shown their worth time and again throughout this pandemic, whether driving ambulances, administering vaccines or supporting patients in hospital."
However, the Royal College of Nursing's director for England, Patricia Marquis, said the deployment meant the government could no longer deny there was a "staffing crisis" in the National Health Service.
"The prime minister and others can no longer be dismissive of questions about the ability of NHS staff to deliver safe care," she said.
"Once the military has been brought in, where does the government turn next in a bid to 'ride out' the wave rather than deal with it?".
Around 1,800 service personnel are already deployed across the UK to support civil authorities in their response to the pandemic.
They include 313 personnel assisting the Welsh Ambulance Service and 96 with the Scottish Ambulance Service, while more than 1,000 are helping the vaccine booster program.
Government figures showed there were 17,988 people in hospital in the UK with COVID-19 as of January 5, up 50 per cent week-on-week and the highest total since February 18 last year.
Infections remain high, with the latest official figures showing there were 179,756 cases of the virus recorded in the UK as of 9am on Thursday.
