When the Kaiser Franz Joseph I is very young, he is saved from enemy fire at the Battle of Solferino by a young Slovene peasant officer whom he elevates to a Barony in honor of his service. Thus begins the von Trotta dynasty, whose heyday is brief and whose decline mirrors that of the Austro-Hungarian Empire itself, already withered and irrelevant before the outbreak of World War I. The Radetzky March begins with the Battle of Solferino, but its focus is on that Trotta's grandson, Carl Joseph, a lieutenant in the Kaiser's army.
Carl Joseph is an unexceptional soldier and a sensitive young man who slowly unravels over the course of the novel. The military is his birthright, but one which he has difficulty being equal to:
For once, Lieutenant Trotta was rebelling against the military laws that ruled his life. He had obeyed since earliest boyhood. And he wanted to stop obeying. He had no idea what freedom meant, but he sensed that it was as different from a furlough as war is from maneuvers. This comparison flashed into his mind because he was a soldier--and because war is the soldier's freedom.
Carl Joseph is beset by disasters, some of which are his own making: Alcoholism, gambling debts--and a weak willingness to cover others' gambling debts--but also the death of his only close friend in an honor duel. The duel itself is a symbol of an old order of prestige that is rapidly passing away, one in which Carl Joseph cannot fit in, but one which threatens to destroy him as it destroys itself.
The Radetzky March is notable for its thorough depictions of Kaiser Franz Joseph, including long passages of the Kaiser's thoughts. (FYI: Franz Ferdinand, whose assassination sparks WWI, is Franz Joseph's nephew and presumptive heir.) These passages, which depict the Kaiser as a complex man approaching senility, are the best in the book, I think:
The night was blue and round and vast and full of stars. The Kaiser stood at the window, thin and old in a white nightshirt, and felt very tiny in the face of the immense night. The least of his soldiers, who could patrol in front of the tents, was more powerful than he. The least of his soldiers! And he was the Supreme Commander in Chief! Every soldier, swearing by God the Almighty, pledged his allegiance to Kaiser Franz Joseph I. He was a majesty by the grace of God, and he believed in God the Almighty, who hid behind the gold-starred blue of the heavens, the Almighty--inconceivable! It was. It was His stars that shone up there in the sky, and it was His sky that arched over the earth, and He had allocated a portion of the earth, namely the Austro-Hungarian monarchy, to Franz Joseph I. And Franz Joseph was a thin old man, standing at the open window and fearing that his guards might surprise him at any moment.
Contrast Franz Joseph's serene prescience with the anxious uncertainty of Carl Joseph and the soldiers in the first passage, the "patrolling soldiers" of the Kaiser's imagination to whom he assigns a kind of power. I doubt very much that this is a historical depiction of Franz Joseph I, but it is compelling one that underscores the great chasm between the perspectives of the powerful and those marked for the trenches.