By Jonathan Duffy BBC News Online

Morale is high among some of our troops heading for the Gulf. But with little public support for a war with Iraq, they may struggle to find the fighting spirit. There's nothing new about anti-war demos. The chants of protesters marching on London, Washington, Cairo, Damascus and Moscow recently are all part of the rich tapestry of emotions in times of looming conflict.

But this time the cries of dissent are not just coming from traditional left-wing pacifist quarters. As Britain and America ratchet up military pressure on Iraq, the anti-war coalition has emerged as a diverse group.

Officers on HMS Ark Royal raise a smile to say goodbye

It includes senior military experts, showbiz stars, Anglican bishops, ethnic community leaders, mainstream politicians and many other establishment figures.

As the Times put it this week, it is "a campaign uniting people who agree about nothing else".

Public support for Britain attacking Iraq has fallen to its lowest in five months, according to a running poll by ICM/Guardian. Just 30% of people would approve of such measures, while 47% disapprove.

Support slipping

In America, support is also slipping. Those in favour of military action to remove Saddam Hussein fell from 62% a month ago to 57%, according to a Washington Post/ABC News poll.

Fighting a war is an exceptional job - wars are won by people doing pretty astonishing things Major Charles Heyman

Click here for map of UK military build-up

The question now worrying strategists is what impact this will have on a fighting force.

As British troops head off for the Gulf, morale appears to be high. That's to be expected, says Major General Patrick Cordingley, a brigade commander in the Gulf war.

"At the moment they are caught up in the excitement of going somewhere and they've got a sense of purpose.

Dying for your job

"But if things get really nasty you start to believe that, actually, you might die out here sometime soon. At that stage you want to know your wife, family and friends are behind you, and the country as a whole believes in what you are doing."

Falklands vet Simon Weston has spoken out against a war

The channels for feeding such sentiment are strong - the British have an excellent forces postal service. And with the post, come the same newspapers that we read at home.

For some, the scepticism has kicked in early.

"Most military people I know who are going feel that they don't have the support of the public," says one former officer from 3 Commando Brigade.

"Indeed, some don't feel that we have a right to invade a country just because we don't like their system of government. This will inevitably affect morale."

Waiting game

And enthusiasm is likely to be dampened further by what has been dubbed the "Sits-krieg" - the long wait for action in the inhospitable desert.

In Vietnam, GIs suffered low morale when support at home dropped

Morale on the front-line is a key weapon in any war effort and, as America's experience in Vietnam in the late 1960s proves, it relies heavily on the support of ordinary people back home.

"Fighting a war is an exceptional job. You can go through the motions but wars are won by people doing pretty astonishing things. It requires the morale, the elan, the esprit de corps," says Major Charles Heyman.

Yet that last phrase could be the key to what might keep British soldiers, if not their American counterparts, fighting strong even without the support of their public.

The regimental system that runs through our military has always fostered great loyalty, or esprit de corps.

"At the end of the day no one is going to go the extra mile for the British army, the government or whoever," says Major Heyman, "they're doing it for their regiment."