Part 1, originally transmitted on BBC1, 20 November 1999

August 1992. Soldiers' civilian lives. Privates Alan James and Peter Skeet celebrate Sandra's birthday. On a night out in Liverpool, they meet a hen party: Skeet flirts with the future bride and James protects Skeet against the prospective groom. Sergeant Andre Sochanik returns to his parents' farm in Scotland to attend his brother's funeral and learn more about his accidental death. Lieutenant Neil Loughrey plans his wedding with girlfriend Emma.

The battalion featuring James, Skeet, Sochanik, Loughrey and Lieutenant John Feeley is recalled as British troops are selected for the United Nations Protection Force to enter Bosnia during a civil war. Loughrey postpones his wedding. Sandra tells James to protect Skeet.

Vitez, Central Bosnia, Autumn 1992. The peacekeepers are welcomed by local children. A briefing explains the peacekeepers' mandate: they cannot take sides and must observe the rules of engagement, not firing unless directly threatened. They note the presence of well-trained former Yugoslav Army troops. Serb advances have rendered the briefing map outdated. The UN's Rik Langrubber predicts that the fighting will produce many refugees.

Feeley's team travel to collect an injured Muslim child. Their armoured Warrior vehicle is obstructed at a mined roadblock, and they resist a search. The peacekeepers help a Muslim family whose house is being burnt out by Croats, but are not permitted to take the family to safety because they must not appear to be assisting with ethnic cleansing. They must only rescue the child, whom Skeet carries across a nearby river.

The Warrior is again stopped at the roadblock, but Feeley kicks away their mines. He is criticised by superiors and reminded to fly the UN, not British, flag. Later, while overseeing refugee movement, James intervenes by pushing a soldier away from a woman whose clothes he tore to look for jewellery.

Christmas. Emma is pregnant; Loughrey is becoming closer to translator Minka. The peacekeepers celebrate Christmas Day with refugee children.

Feeley dines with Almira Zec and her husband Naser, one of few Bosnians left at a factory that had been run by Muslims and Croats. Almira remembers the beauty of Sarajevo before it was attacked, forcing their enforced departure. She thinks the area is cursed.

Peacekeepers are called to escort an ambulance for a pregnant woman. When local troops use Feeley's Warrior as a shield, they are shot at and Skeet is killed.

James and the others want to retaliate but are not allowed. James visits Skeet's body.

Serbs stop the peacekeepers at a bridge, preventing them from reaching their bombing targets until tomorrow. Feeley believes they will be powerless to help by then. Responding to Loughrey's frustration, Langrubber criticises the British Army for wanting to smash through. Serbs check IDs. Sochanik's Polish background prompts inflammatory insults. Sochanik does not respond but the translator realises that he understands the language. The Serbs also insult Lieutenant Engel's Jewish heritage.

The next day, the Serbs only allow four vehicles through, which angers Loughrey because they have 24,000 people to attend to. They are reminded to only take the most seriously injured. The peacekeepers realise a massacre is imminent.

In an attempt to delay the Serb attack, locals hold the peacekeepers' vehicle: they must either drive over the people or stay to die with them. Sochanik believes the world will only notice the massacre if the peacekeepers die too. Sochanik's father is a Serbian, his mother Polish - they met undergoing forced labour in wartime and, feeling unsafe after liberation, moved to Scotland.

James amuses local children by covering his head in shaving foam. There are explosions. The Serbs claim the Muslims are shelling themselves. Telling the locals the peacekeepers are powerless to help, Captain Gurney orders withdrawal, frustrating some of his men.

James smuggles a youth in a Manchester United shirt into their vehicle. Serbs stop the vehicle and demand to search it. Gurney calls them war criminals and refuses, but Langrubber tells him they must be unemotional and neutral. James and the others disguise the youth but he is discovered and Gurney orders them to give him to the Serbs. After a confrontation in which James threatens the Serbs, they take the youth away. As the peacekeepers drive away, James cries.