The possibility of declaring someone a hostis (enemy) of the Roman state was available for a relatively short period of time, with attested cases from 88 to 40 b.c. Nevertheless, it was an important weapon in the civil wars of the period. This book is the first monograph dedicated to this concept, and therefore in itself a useful contribution to our knowledge of the late Republic. Furthermore, Allély's book gives a clear analysis of the legal and political aspects of the hostis-declaration. She starts out by investigating the origins of the concept. The Gracchan period had seen an important innovation in Roman politics, the senatus consultum ultimum (SCU). This, however, had no legal consequences for individuals who posed a threat to the state, and the possibility of declaring them hostis was therefore necessary to exclude them legally. Sulla was the first to use the hostis-declaration against Marius and his supporters in 88 b.c.; usually, the official declaration was made by the Senate, with confirmation from the comitia tributa. The connection between the issuing of the SCU and the hostis-declaration remained close: in about half the attested cases, both decisions were made together, as table 2 (151) demonstrates.

A. traces in chs 1–3 the various hostis-declarations throughout the first century b.c., including those against Sulla in 87 b.c., Lepidus in 77 b.c., Catiline in 63 b.c., Caesar in 49 b.c., Milo in 48 b.c., Antony, Lepidus and Dolabella in 43 b.c., Octavian and L. Antonius in 41 b.c., and Salvidienus Rufus in 40 b.c. The last case was an anomaly, since Rufus was accused of treason, rather than of bringing armed force against the state; probably Octavian used Rufus as a warning to others not to betray him. After this, the hostis-declaration was no longer used. Octavian presented the war against Antony and Cleopatra simply as a foreign war, which better served his purpose of ‘restoring the Republic’. As ch. 3 discusses, the late 40s b.c. saw the ‘banalisation’ of the hostis-declaration: not only rebellious individuals, but their whole armies were declared enemies of the state. This clearly acknowledged the growing importance of the army in politics of the period: if it was the support of the armies that made warlords victorious, then the soldiers should also suffer the consequences of supporting someone who tried to attack the Roman state.

Ch. 4 discusses the ‘view from the side of the hostes’. Being declared an enemy of the state had important legal consequences: the loss of citizenship, which brought with it the loss of magistracies, priesthoods and military commands, as well as the confiscation of property and the destruction of one's house, as a symbol of the end of one's gens. There was no automatic death sentence attached to the declaration, but anyone who killed an enemy of the state would not be punished. This meant that people with ambitions in politics, such as Sulla and Caesar, were no longer legitimate commanders and politicians when they were declared hostis. Sulla, who was in the East in 87 b.c., simply ignored the declaration and continued to behave as a legitimate proconsul; when he returned to Rome with his army, the Senate was quick to withdraw the hostis-declaration and ratify his acts in the East. In any case, especially in the 40s, the situation changed so quickly that in most cases not all the measures could be carried out, and many hostes did not lose their property. They usually retained their commands, because these provided the best possibility of military victory, which (in turn) allowed them to have the declaration withdrawn, as Sulla had done. Caesar similarly retained his army, marched on Rome and had the hostis-declaration annulled by the Senate. Since many hostes did not lose their property, they could easily be reintegrated into social and political life; furthermore, since a hostis-declaration did not apply to children (contrary to a proscription), the children of former hostes could also easily take up a political career — making the Lepidi the only father-son duo to both be declared hostes.

A hostis-declaration could be useful for those aspiring to honours, such as triumphs and trophies: since the defeated men were enemies of the state, it was easy to claim that the war was an external rather than a civil war. Cicero, for example, was given a supplicatio by the Senate, which was normally only granted in the case of external wars. He furthermore suggested that since Catiline had been declared an enemy, a triumph might have been appropriate as well. Caesar on other hand never declared the Pompeians hostes, probably because it did not fit his policy of clementia. The term hostis could also be used as a rhetorical tool, in order to emphasize the danger presented by certain people. Thus Cicero in his Philippics repeatedly called Antony hostis, in order to pressure the Senate into starting a war against him.

The book contains a useful catalogue of all known and supposed hostes, with detailed bibliographical details on each man. A. also investigates in each case why someone was declared hostis and the effects on their future career. This catalogue in itself shows the flexibility of the concept: in many cases the declarations were quickly withdrawn and the men reintegrated into political life. It is clear from this well-written book that the hostis-declaration was a useful tool in the civil wars, but that its usefulness was limited in periods of public chaos, and that other methods of removing opponents (for example, proscription or exile) were more effective. The book has a clear layout and only a few typographical errors; the modest price makes it well worth buying for anyone interested in the political and legal history of the late Republic.