The Legal Theory Bookworm recommends War and the Law of Nations: A General History by Stephen C. Neff. Here is a description:
This ambitious volume is a history of war, from the standpoint of
international law, from the beginning of history to the present day.
Its primary focus is on legal conceptions of war as such, rather than
on the substantive or technical aspects of the law of war. It tells the
story, in narrative form, of the interplay, through the centuries,
between, on the one hand, legal ideas about war and, on the other hand,
state practice in warfare. Its coverage includes reprisals, civil wars,
UN enforcement and the war on terrorism. This book will interest
historians, students of international relations and international
lawyers.
And from the reviews:
‘The scope of Neff’s project is majestic, and his scholarly rigor in
marshalling evidence on the subject of war from antiquity to today’s
war on terrorism is impressive. The book is written in an engaging
manner likely to appeal to both law of war experts and generalists
alike. Neff does not oversimplify, however, and handles even complex
legal questions in a sophisticated and nuanced manner. He accordingly
makes a substantial contribution to our understanding of the phenomenon
of war.’ Allen S. Weiner, The American Journal of International Law
‘[Neff’s] latest book is a spirited and enlightening addition to this
literature … The narrative, written with brio and wit, is a delt
synthesis of a seemingly vast array of state practice and scholarly
doctrine stretching over many centuries. Of particular interest,
originality and value is Neff’s treatment of ‘imperfect wars’ or
‘measures short of war’ … spirited and sparkling book, which
thoroughly deserved its Honourable Mention in the 2007 American Society
of International law book prizes.’ –Cambridge Law Journal"The scope of Neff’s project is
majestic, and his scholarly rigor in marshalling evidence on the
subject of war from antiquity to today’s war on terrorism is
impressive. The book is written in an engaging manner likely to appeal
to both law of war experts and generalists alike. Neff does not
oversimplify, however, and handles even complex legal questions in a
sophisticated and nuanced manner. He accordingly makes a substantial
contribution to our understanding of the phenomenon of war."
–Allen S. Weiner, Stanford Law School The American Journal of International Law