Sir Menzies Campbell has been asked by Liberal Democrat leadership contender Nick Clegg to lead a review of the welfare of Britain's troops and their families.
The former party leader has kept a relatively low profile since stepping down in October.
But Clegg said it is time for a commission to examine the state of the Military Covenant.
"I have asked Ming Campbell, a politician with an impressive track record on foreign affairs and defence, to chair an investigation into the status of the Military Covenant of this country," he said.
"This commission will consider both short-term factors and the longer-term strategic view about the future demands that will be placed on our armed forces."
Clegg also outlined a series of priorities for restoring the covenant, including withdrawal from Iraq, a new strategic defence review and military-only hospital wards.
He also called for greater clarity on what support military families should expect and urged reform of military inquests.
"It is one of the gravest accusations that can be levelled, but there is growing evidence that this government is failing to provide adequate care and support for our troops abroad and their families at home," said Clegg.
