"The strong do what they can and the weak suffer what they must" — stated Thucydides (460-395 B.C.), the Greek historian and Athenian general who sometimes is called the father of political realism, which holds relations between states to be based on might with little consideration for right. The still-snowballing controversy over industrial-scale global U.S. spying is not a bad illustration.
The ancient dictum has been subject to two trends whose lines are now intersecting. The first is a gradual but unmistakable hemming in of might by right over the course of human history.
From one point of view, the story of human civilization is the history of efforts to tame, contain and reduce the use of organized violence both within and across national borders. To reduce internal violence, states were given the monopoly on the legitimate use of force. To reduce international violence, the right of states to wage wars has been progressively restricted to continually tightening circumstances.