Hugo Grotius 
On the Law of War and Peace 

“On The Law of War and Peace” was translated into many languages, and most law schools adopted it as the basis of the right of nations. Princes and statesmen consulted the book, and just as Alexander the Great always had a copy of Homer’s 'Iliad, ’ so the great Gustavus Adolphus always had with him a copy of Grotius’ work, to remind himself that even the most successful general must respect some laws. Grotius’ strength lies in his moderation and in the fact that he quotes copiously from the best authorities to fortify his views .