In March 1939, two old veterans, Chelsea Pensioners, disparage young soldiers as they recall their own glory days in the Duke of Glendon's Light Infantry (the 'Dogs'). Meanwhile, four civilians carry on with their lives in the nervous pre-war climate. Brewer, a bumptious Cockney and dedicated complainer, tends the boiler at the Houses of Parliament; Beck, ever optimistic, is a travel agent clerk. Lloyd, quiet and distant, is a rent collector, while Perry, newly married, fits his Territorial Army duties in between work as a garage mechanic.

By May 1941 the group has been summoned for war duty with the Duke of Glendon's; they meet en route to the Army camp at Hacklefield. Others encountered include Davenport, a pompous store manager, and his callow assistant Parsons; Luke, a Scottish farmer; and Stainer, a cocky car salesman, a little the worse for drink, who spills tea over a frosty sergeant at the Crewe station buffet bar. At Hacklesfield, Perry, now a commissioned Lieutenant, is placed in overall charge of the No 9 platoon, working with Fletcher, the sergeant from Crewe, an Army regular. When Lloyd goes to Perry to complain of Fletcher's rough treatment during training, Perry suggests that Fletcher is probably only doing his job, something confirmed at a Sergeant's Mess party when Fletcher praises the group's potential: "We haven't a dud there, sir."

Beck alone remains cheerful; the other conscripts face their assignments and deprivations with grumbles and indignation. Perry encourages them to participate in a forthcoming regimental concert, but only Beck volunteers. Backstage, Perry hears news about Parsons, who has been arrested at the train station by the Military Police as he tried to leave for London. Parsons explains that he's worried about his pregnant wife, who is being bullied over unpaid Hire Purchase payments. As a deserter he expects punishment; instead the Army arranges for financial help and gives him 48 hours' leave.

Parsons is now equable, but with most of the rest army life still riles. During a tiring exercise, the malcontent Lloyd takes the initiative and lets the group be 'killed' by the opposing side, in order to return quickly to barracks. Perry sternly berates the platoon for letting down the regiment's name, though he does not report them to the battalion's chief, Captain Edwards. Relations with Perry remain frosty until the two sides meet by chance at the home of Mrs Gillingham, who on Sundays offers tea, scones, and hot baths. By the time of their return home on leave, team spirit is stirring in the conscripts.

July, 1942. The Chelsea Pensioners continue to berate the modern army, and fret over the Dogs' inaction. The platoon, meanwhile, is told it is to go on a special two-month course, with leave being brought forward. Some know, and some suspect, that this means action abroad. On a troopship heading south, Perry explains the plan: with Rommel in retreat after the victory at Alamein in October, the Dogs will form part of the Allies' North African invasion force. But it is not to be: in the Mediterranean they are hit by a German torpedo, and after battling fierce flames and losing supplies they have to abandon ship.

March, 1943. The Chelsea Pensioners scan the war news and grumble at the Government, while the platoon's wives, meeting socially, share what little news they know about their husbands. The platoon is now in a Tunisian village, some way from any fighting, and accommodated at the Café Rispoli, much to the pacifist owner's distaste - though he mellows after joining in a game of darts. The group man a look-out trench, but are restless and bored. Action suddenly arrives; the Germans encroach, and Perry's team are ordered back into the village to combat the attack there. Even the café owner Rispoli takes up arms. furious bombardment and gunfire, Perry's group attach bayonets to their guns and march out through the smokescreen to continue the battle. Back in London, the two Pensioners finally read the good news about the Dogs they have long wanted.