Extensive cuts to the British Army and Navy were announced yesterday at a time when many are already complaining that operations in Afghanistan and Libya are leaving them stretched.

Yesterday 5000 soldiers were told that they were in a perilous situation and a fifth of them would be redundant by September. Meanwhile, 5600 Royal Navy personnel were told that 1600 of them will lose their jobs.

The Brigade of Gurkhas was told it would not enjoy the protection of other key front-line posts. Their "loyalty" has left it overstaffed and needing to find 150 job cuts.

Sources in the Government protested that no one wanted to make the cuts but "we have no choice given the £38 billion ($80 billion) black hole left behind at the MoD by Labour".

Under the Strategic Defence and Security Review (SDSR) the military has been told that it must cut 17,000 staff by 2015 and 11,000 will be redundancies.

Colonel Stuart Tootal, who left the Army after leading 3rd Battalion, the Parachute Regiment, in Helmand said: "The Government has admitted that the SDSR was conducted at pace. It should remain a dynamic process whereby it is kept under review. This is an opportunity to pause and reflect, to take a statesmanlike look and consider how deep these cuts should be."

Yesterday, the Army and Royal Navy announced who would be targeted in the first tranche of four, a month after the Royal Air Force listed its figures.

"The impact on individuals will be varied," said Brigadier Richard Nugee, adding that 150 fields were to be targeted in the first tranche of a process that will see the Army reduced by 7000 by 2015. "Some will see it as an opportunity. For others it will be a time of uncertainty and disappointment."

The Army is hoping that half its 1000 cuts will be from voluntary redundancies, though not all will be accepted, before compulsory redundancies are selected "to maintain the right balance of skills" and announced by September 1. A quarter will be officers.