As darkness falls, legionnaires in armoured personnel carriers (APCs) fan out across the airport, guided by monitors using night-sights or thermal cameras which pick up body heat. This is probably the most controversial part of their mission as defined by a United Nations mandate.
Last week, the 2nd Foreign Parachute Regiment, the 2e REP, the toughest and most glamorous French regiment, blue helmets replacing their white kepis, took over Sarajevo airport from the French marines in the UN Protection Force (Unprofor) who secured it and opened it to relief flights six months ago.
'They are going to find it is a big moral problem,' said a marine NCO. 'Sometimes you find yourself turning back a young mother with a small baby.' Under UN rules, the troops have to observe total neutrality and not be seen to help anyone, however defenceless. In the two-and-a-half months since the crossings started, the number caught has usually been between 200 and 300 a night. On one night recently, a record 500 were found.
On Monday, the APCs were on standby from 5pm. Very quickly, a radio operator told the patrols 'there are a dozen personnel behind the perimeter fence'. Shortly afterwards 10 men were caught and put up against the APCs to be frisked under the vehicles' spotlights with sporadic artillery and mortar fire as background noise. Three or four were carrying backpacks and were dressed in military-style clothing.
'We take them back to the perimeter and then they try again,' a legionnaire said. 'Sometimes we catch the same people four or five times a night.' Of the 339 picked up on Monday night, none carried weapons and 47 were women.
Two hundred legionnaires, from 65 different nationalities, arrived in Sarajevo on 13 January. Another 200 are to join them this week from their base in Calvi, Corsica.
With their basic mission to ensure airport security and protect the convoys of humanitarian aid which serve Sarajevo and the surrounding countryside, the Foreign Legion considers it has added a touch of class to a mission in one of the most hair-raising parts of the world.
When a television crew was lunching in the base, Colonel Michel Poulet, the 2e REP's 44- year-old commanding officer, was nervous that the cameraman might film his men eating off the metal trays left by the marines. Their usual crockery, marked with the regiment's crest, was still on its way. Enough, however, was already available for the senior officers.
With waiter service and a wicker cheeseboard carrying six varieties of cheese on a bed of lettuce leaves, the officers drank no wine at lunch but a palatable St Emilion accompanied dinner.
'The Legion does everything better,' said Colonel Jean-Jacques Kowalski, the regiment's chief medical officer, as he asked a visitor to hang up his bullet-proof vest on a rack specially made for flak jackets. Col Kowalski's bedroom in the infirmary, set up in an airport warehouse, was partitioned from his neighbours by blankets. Soon, he says, he will have plywood to improve the arrangement.
All ordinary legionnaires are, true to legend, tough and hardened soldiers. Of the 2,000 or so men who try to join the Foreign Legion every year, only one fifth are accepted. Of those the 2e REP gets the top 20 per cent.
In the Sarajevo battalion a handful of soldiers are from Britain and Ireland. Ground rules set by the Legion forbid putting personal questions to them, but the pattern for the British soldiers seemed to be that they had already served in the British army, usually in Northern Ireland, and joined the Legion to escape unemployment or because their British regiments were being disbanded.
A former Grenadier Guardsman from Hackney said he joined because his application to the British Transport Police was taking a long time being processed. With two and a half years of the minimum five-year term still to serve, he said he was still hoping to join the transport police eventually.
In an APC accompanying a convoy of food aid through Serbian lines to the Muslim suburb of Dobrinja, Tony Redman of Bristol manned the vehicle's 20mm cannon. When the APC parked by a wall - added protection from the shells which were falling on the area - he opened a door and called 'Hey, Charlie]' The first of a group of Muslim boys who ran up to the APC received a bag of food the soldier had saved from his rations.
The other soldier in the back of Tony Redman's APC was French, 'or rather Swiss. To join the Legion, I said I was Swiss.' He had thrown some sweets to children through the APC's tiny window. When an old man with a stick doffed his hat on the other side, arriving too late for any of the goodies, the legionnaire shook his head.
The Frenchman's nationality fib enabled him to circumvent a regulation that 52 per cent of the Foreign Legion must be foreigners. Legionnaires are entitled to lie about elements of their biography, changing parts or all of their name or details such as date or place of birth so as not to be traced. They go into an administrative limbo and have no official civil identity. Because of this, they cannot open bank accounts and are paid in cash.
'We hear details of their lives when they are depressed or after they've had one beer too many or at Christmas,' said one officer. 'We have to celebrate Christmas with the men, which our wives and children often don't understand.' French officers of the Foreign Legion are all volunteers.
'The Legion is a train which never stops,' said a captain. 'The men try to jump on. Then it is the job of the officers to pull in those who manage to hang on and to find them a comfortable seat.'
Col Kowalski said he received Christmas cards from former legionnaires. 'One, James in Ireland, wrote this year 'Keep your head down in Sarajevo',' he said.
Officers in Sarajevo said a strict questioning procedure eliminated most undesirables, and they did not believe serious criminals could get into the Legion easily these days. They said, however, that a number certainly had a record of minor offences from which they wished to escape. 'They are questioned very carefully about themselves in their own language before they can join,' one said.
Once in, those who cannot speak French are attached to a French-speaking legionnaire who teaches them 'the language of survival which enables them to live from day to day,' said Major Charles Guermeur, a Breton with 11 years' service in the 2e REP. 'Every course of instruction in their three-month basic training becomes a language lesson. The instructor handling a rifle shouts out 'la crosse' (the butt) and all the recruits repeat the words out loud.'
After a French examination at the end of training, the recruit becomes a legionnaire but language courses still continue. 'One of the oddest things I ever saw was a German sergeant at a checkpoint helping a Chinese legionnaire with his exercises,' said one officer.
In Sarajevo, Major Guermeur said the Foreign Legion had made no attempt to keep Yugoslavs out of the volunteer force sent to guard the airport. 'We have about 10 including two regimental sergeant-majors,' he said. 'They have been in France a long time and, although we feared there might be friction, there has been no trouble among our Yugoslavs.'
The nationalities trends in the Foreign Legion change with the times. 'In the 1970s, we had a lot of Portuguese as Angola was decolonised,' one officer said. 'Then there were a lot of British after the Falklands. In recent years, we have been getting a lot of East Europeans.' Another officer added: 'We had a lot of Japanese coming after a book on the Legion was published in Japan.'
The mix of strict selection, tough training, different national backgrounds and discipline enabled the 2e REP to be 'a feline and supple force', Major Geurmeur said.
In the next few weeks, the talents of a regiment which has served in Chad, Rwanda and Beirut over the past decade, as well as carrying out the spectacular 1978 parachute drop over the Zaire town of Kolwezi to rescue European residents during a rebellion there, may well be put to a very hard test.
Unprofor officers fear that an eventual international intervention in Bosnia will make the Sarajevo force a prime target for Serbian gunners. 'If the worst comes to the worst, the French can fight their way to the sea,' about 80 miles away, a British officer with the UN observer mission monitoring the fighting said. 'They shouldn't find it too difficult.'