Lines of Courage follows five teenagers over the course of four years during World War I, from June 28, 1914 to November 11, 1918. Each chapter is dated chronologically, and corresponding historical events are included in the narrative. In the Author’s Note at the end of Lines of Courage, Nielsen offers additional insight into selected historical events that are especially relevant to her novel, including the assassination of Archduke Franz Ferdinand, the Battle of Verdun, or the Russian Revolution.

In short, mounting tensions between European nations at the beginning of the 20th century erupted when Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, was assassinated in Serbia in 1914. This led the Austro-Hungarian Empire, backed by Germany and the Ottoman Empire, to declare war on Serbia, which soon allied itself with Russia, France, and Great Britain. The United States joined the Allies in 1917, while the Russian Revolution arguably undermined Russia’s position in the war. After the collapse of the German and Ottoman Empires, the armistice ending World War I was signed on November 11, 1918, in Paris, leading to the creation of several newly independent countries, like Poland, Czechoslovakia (the present-day Czech Republic), and Yugoslavia.