Ancient Warriors is divided as follows: overview of specific armies; short biographies of military leaders; overviews of battles throughout history. The book covers the Bronze Age until the 14th Century CE and features armies such as the Mayans (pp. 12–13), the Romans (pp. 24–28), the Huns (pp. 34–35), the Vikings (pp. 42–43), and the Samurai (pp. 50–51). These armies are arranged chronologically and are described along with their respective military leaders such as Ramesses II (pp.16–17), Alexander the Great (pp. 22–23), the Trung Sisters (pp. 32–33), Tomoe Gozen (pp. 52–53) and Joan of Arc (pp.56–57). 

Illustrations of historically-renowned conflicts are interspersed throughout the book. This serves to present these armies in action in their respective environments. These conflicts include: The Greco-Persian Wars (pp. 20–21), The First Punic War (pp. 26–27), the battle of Yarmouk (pp. 40–41), and the battle of Crecy (pp. 54–55).

Several chapters focus on biographies of great leaders such as Ramessess II of Egypt, and Tomoe Gozen of Japan. One such leader is Alexander the Great. The page adjacent to his biography shows Alexander in his tent pouring over a map of Europe and Asia. He is shown to be relatively young, with mid-length blonde hair over his Macedonian military uniform. Alexander’s biography paints him as "probably the greatest General who ever lived." A focus on Alexander’s military success is attributed to his use of mixed units, the Companion cavalry that sowed terror in his enemies.

The use of illustration within the book compliments the short paragraphs of text which offer context for the drawings. An example of this is the Legendary Battle: The Greco-Persian Wars. These two pages have a total of three paragraphs, one outlining the background to the war. The illustration dominates the spread of two pages. The focus is placed on the Battle of Salamis, where Lillington depicts a turbulent scene of a Greek naval scene. Readers are enable to distinguish between the two warring sides due to the contrast in their clothing. A decision has been made to include red horse-hair crests on each hoplite’s helmet. This could either be to provide a uniformity to the painting, or to play to the ideas of "Greekness" within popular culture typified by Frank Miller’s graphic novel 300. The focus and intensity with which the illustration is presented shows the clamour of battle, with background scenes presenting similar scenes of conflict.

Illustrations of historically-renowned conflicts are interspersed throughout the book. This serves to present these armies in action in their respective environments. These conflicts include The Greco-Persian Wars (pp. 20–21), The First Punic War (pp. 26–27), the battle of Yarmouk (pp. 40–41), and the battle of Crecy (pp. 54–55).

In addition to depicting particular battles, the book focuses on the individual soldier. A page offering a description of the Roman Legionary gives the reader an overview of their panoply and tactics. An introductory paragraph focuses on the uniformity, discipline, and coordination which allowed for their military successes. An annotated illustration of a soldier presents each element of the panoply with their native language and the English equivalent name e.g Scutum / Shield, or O-yoroi/full armour. The depth of illustration allows the reader to see the intricacies of the armour. On the adjacent page, the focus on tactics demonstrates the Legion’s tactics in action. An illustration presents native Germanic peoples in front of a forest battleground barraging the Legion with arrows. The Legion is shown in the Tortoise formation to enable it to deflect these missiles. The paragraph below the illustration explains the benefit of the formation and the reason for the adoption of this tactic. Thus, illustration and text complement each other and readers are provided with a context for the peoples, weapons and armour.

The penultimate page, titled The Evolution of Weapons, explores the various developments in materials and their impact upon weapon types. The book includes illustrations of a bronze sword from the Bronze Age, a Roman iron sword, and a Japanese steel katana. The varied cultural backgrounds of these weapons show the reader the variety of design that can be offered from different materials and cultures. A focus is placed on obsidian with an illustration of an obsidian knife and spear used by the Maya people and a description of the macuahuitl club. 

The final pag, The Evolution of Armour, focuses on the evolution of armour types with details of the protection offered and design details. The four armour types are: tanned skins, lamellar armour, scale armour, and plate armour. Following the different cultures detailed, the reader is able to place the varieties of armours with their respondent armies. A specific focus is placed on a suit of bone armour discovered by archaeologists in Siberia. By placing such vastly different armours side-by-side the reader is able to see the developments of these armours shaped by centuries of conflict.