In a small British town during World War II, a group of elderly men forms part of a local defense unit known as the Home Guard. These "soldiers" are mostly retirees, groups of neighbors, and a couple of enthusiasts who, despite their limited training and questionable skills, are determined to protect their home from any threat, even a potential Nazi invasion. Captain Mainwaring, a somewhat arrogant but good-hearted man, is in charge of leading this peculiar group, often dealing with their egos and incompetences.
The situation becomes more complicated with the arrival of the new secretary, the charming and cunning Catherine, whose presence stirs up some jealousy and tension among the men, who try to prove their worth both on the battlefield and in the game of love. As the unit trains with hilarity and some blunders, a German spy looms over the town, forcing the little men to spring into action to protect their home.
With an air of classic British comedy, the film explores not only the wartime challenges faced by the protagonists but also their personal relationships and the importance of camaraderie. As the story unfolds, the unit shows that although they may be a disaster in the field, their heart and determination are all that is needed to change the course of the local war and prove that courage knows no age.