Putting Nature and Nations Asunder 149ligerents regarding the conduct of war are identical, without regard to which
side might have been at fault in instigating the confl ict.
Th e third major fi gure in writings on the laws of war was Alberico Gen-
tili, who, like Belli, became largely forgotten until rediscovered in the nine-
teenth century (in his case, by the En glish international lawyer and legal
phi los o pher T. E. Holland). Gentili was a native of Italy (from the March of
Ancona) who, again like Belli, studied law at the University of Perugia. As
he adhered to the Protestant faith, he left Italy for En gland, where he became
a professor of civil law (i.e., Roman law) at Oxford in 1587. His principal
contribution to international law was a massive treatise on the laws of war
published in 1598. Th is was a much more substantial work than that of ei-
ther Belli or Ayala, as it treated the problem of war within a comprehensive
framework of natural- law thought.
According to Gentili, a war could be just on both sides, provided that
each side had “a plausible ground” for resorting to hostilities. Th e immedi-
ate practical eff ect was to accord an equal entitlement to both sides to exer-
cise the rights of just-war makers. He even identifi ed this principle of even-
handed treatment of belligerents as the clearest of all of the laws of war. In
explaining the rationale for this conclusion, he resorted to the imagery of
litigation, comparing the impartiality of the laws of warfare to the impar-
tiality of the civil law in “contests of the Forum.”
A conspicuous sign of the new outlook on warfare was the stress of these
writers on formal aspects of warfare over substantive questions of the justice
of the underlying dispute. In par tic u lar, there was now a great deal more
emphasis than before on the need for a public and explicit declaration of
war— though no specifi c form was prescribed. Th is, too, was an indication
of the fading grip of medieval just-war theory and the gradual trend toward
concentration on what came to be called the formalities (or the conduct) of
war, rather than on the lawfulness of the resort to war. Gentili held the issu-
ing of a declaration of war to be a requirement of natural law. Again resort-
ing to the analogy of litigation, he compared a declaration of war to the
ser vice of a writ in a civil lawsuit.
Another important change from the Middle Ages was a new emphasis on
the manner in which war was conducted. Increased attention was paid, for
example, to the need to enforce discipline among troops. Nearly a third of
Ayala’s treatise was devoted to the topic of military discipline, which in his