Kitab al-Siyar (2 vol., Fazari)كتاب السير

Considered one of the oldest books on International relations, this book can be considered historical in the nature it is written or more properly as a book of legal rulings. Mainly it deals with matters relating to how Muslim governments should deal with non-Muslim regimes. Legal rulings of various scholars (Imam al Awzai, Shaybani,Sufyan, et al) are recorded throughout to provide interpretation on weighty matters while in other sections there are mere reports of happenings in different circumstances with his or another scholars' opinion approving or disapproving. Excellent source for early Muslim History and international relations.
This edition contains an extensive introduction to the historical context/use of the book, commentary, editing by Dr. Faruq Hamdah.