The novel An Ice Cream War takes place between the years 1914 and 1919. The action takes place mostly in the European colonies of East Africa and England. People of a variety of backgrounds are affected by the largest and most costly of wars in world history up to that time. Some of the characters expect war, and some doubt it will occur. None of the characters have any idea how devastating the war will be to everyone, even those far from the battlefield.

The novel begins in German East Africa in the months prior to the outbreak of war in Europe. Walter Smith owns a farm across the border in British East Africa, and he has traveled to Dar-es-Salaam to purchase coffee seedlings to plant on his farm. Walter is an American who lives in Africa and enjoys a pleasant relationship with his distant neighbors, British and German alike.

Around the same time a young man in his late teens, Felix Cobb, returns home from boarding school for the wedding of his older brother, Gabriel. Gabriel is a professional soldier, a captain in the British Army, but Felix is more of an intellectual currently dabbling in notions of pacifism. Despite their differences, the brothers share a wonderful relationship and have a great deal of affection for each other. Gabriel believes a war between Great Britain and Germany is coming, and he believes it will be a glorious affair with bands and medals. Felix believes the people of the world are having far too much fun to take time for a silly war.

Gabriel's honeymoon is cut short and he is sent to war. His new bride remains home in England where she becomes close friends with Felix. Soon after arriving in Africa Gabriel is severely wounded and has to reside in a German hospital. Felix's friendship with his sister-in-law continues to grow until it is cut short by tragedy. Partly out of guilt and partly out of grief, Felix decides to cast aside his belief in pacifism and join the army in the hope that he can go to East Africa and find Gabriel.

Felix's path to German East Africa is anything but direct, but after much time and many side routes he meets Walter Smith. Walter is seeking the German officer he believes is solely responsible for the destruction of Walter's farm, and Felix is still searching for his brother. Walter and Felix soon discover that their goals have much in common, and they join forces in their search. The meeting of Walter and Felix brings together all of the principle characters that have been separate for much of the novel.

Through the course of the novel some issues are resolved, but few if any are resolved in ways that the characters want or expect. Regardless of the particular beliefs they held concerning armed conflict between nations before the outbreak of war, their beliefs change, and they come to realize that no one anywhere is isolated from or immune to the effects of war.