They joined Shrewsbury & Telford Hospital NHS Trust (SaTH) on Monday.
It is understood that they will be supporting the trust's emergency departments at both Royal Shrewsbury Hospital and Princess Royal Hospital Telford.
The NHS said that there are 400 army personnel who are helping at other hospital trusts – not just SaTH.
They are understood to be a mix of combat medical technicians and soldiers performing general duties.
Their roles will include facilitating with ward activities, family liaison between clinical teams and families of patients, estates and porter duties.
A spokesperson for the NHS said: "The NHS is grateful to the 400 military personnel working in hospitals in the Midlands and London, alongside doctors, nurses and others who have returned to the NHS front line and tens of thousands of St John volunteers working across the country.
"The NHS has 50,000 more staff now working in the health service than a year ago all working round the clock to respond to unprecedented pressure on the NHS.”