Rome's wars reach us almost entirely through later writers, working from sources that are now lost. So every account in these volumes carries a grade, and each chapter's Editor's Notes set out what the grade rests on.
The four grades
The grades range from A (strict eyewitness or contemporary archival access) to D (suspect attribution or problematic transmission); the great majority of entries in this volume will receive grades of B or C, reflecting the retrospective nature of nearly all surviving sources for the period.
From the Proem to Book I
AThe strongest of four grades: strict eyewitness or contemporary archival access
BThe second of four grades, from A (eyewitness or contemporary record) to D (suspect or problematic)
CThe third of four grades, from A (eyewitness or contemporary record) to D (suspect or problematic)
DThe weakest of four grades: suspect attribution or problematic transmission
In the text a grade appears as a small seal, BGrade B, beside the claim or source it qualifies. A single event can carry two grades: the bare fact of a battle may be well attested while the speeches before it are not.
Tiers: how many hands between us and the event
The notes also place each source in a tier. In the notes' own examples, T1 marks the closest witnesses, such as the fragments of Hieronymus of Cardia; T2 the historians who worked from them, such as Polybius, or Livy writing through lost annalists; and T3 the later compilers and epitomes, such as Florus and Eutropius.
An evidence file
Each chapter closes its main episodes with an Editor's Note like this one, from Book II:
The Crossroads
At the end of each chapter you stand inside one of its real decisions, at the moment it was made, knowing only what those present could know. Each course open to them is weighed by your own inner voice. Nothing is scored. Only after you decide do you learn what was done, and on what evidence. Then, if you choose, you can walk the decision through at every scale, from your own conscience to our own time.