Just War Part 9: Hugo Grotius

Hugo Grotius

By the time Hugo Grotius was born in 1583, Catholicism had lost it’s monopoly on faith in Europe. Martin Luther nailed his theses up in Wittenberg, the Reformation spread, giving birth to Protestantism – and then Protestantism split into factions of its own.

Grotius was Holland’s attorney general and a member of the Remonstrants, a group of upper-class citizens sympathetic to Jacobus Arminius’ “tolerant Protestantism.” The group was in constant conflict with the Gomarists, orthodox Calvinists led by Franciscus Gomarus, a group most of the nations population and ministers sided with – possibly because the group was led by Prince Maurice.

In 1618, Prince Maurice, using the nation’s military, arrested several prominent Arminians. Some were executed and Grotius was sentenced to life in prison. He escaped and spent most of his remaining years in France.

It was there that he made his contribution to Just War thinking and earned his title “Father of International Law” by publishing De jure belli ac pacis (On the Law of War and Peace).

“Although the paternity of international law belongs as much to Victoria and Gentili, yet Grotius is still considered the most significant writer on international law.”(1)

Grotius wrote…

…fully convinced…that there is a common law among nations, which is valid alike for war and in war, I have had many and weighty reasons for undertaking to write upon this subject. Throughout the Christian world I observed a lack of restraint in relation to war, such as even barbarous nations should be ashamed of.

This “common law” is what Aquinas had called “natural law” – a way that seems right to all people. Grotius further developed the idea of common law, stating outright that consideration of God (or his revelation) was unneccessary when determining if a war was just or not.

…even if we should concede that which cannot be conceded without the utmost wickedness, that there is no God, or that the affairs of men are of no concern to Him.

Grotius argued that our criteria for Just War must be independent of all religion. After all, battles were being fought across Europe between Arminians, Calvinists and Catholics. An independent criteria not founded on faith had a chance, he reasoned, to bring peace to those divided by faith.

Just War doctrine had not been birthed from scriptural exegesis or reflection on the nature and will of God in the first place, but Grotius was the first to declare that it shouldn’t be.

By ditching even the illusion that Just War theory had a faith foundation, Grotius was able to focus his Just War criteria on just cause and give very little attention to right authority and right intention – unlike previous Just War thinkers.

This was a shift away from the inner religious realm of conscience that had been a prime concern of Vitoria toward the exterior and observable. This move strongly influenced later thinking about war.(2)

This emphasis on externals is a mark of the secularized just-war doctrine. (3)

“In the absence of an agreed moral theory,” one U.S. Airforce historian writes, “it made sense to keep to what everyone could see.”(2)

Not only did Grotius separate Just War thought from religion, he also defined more broadly than ever who the enemy is. Grotius considered an entire hostile nation, with all its citizens, the enemy. War was no longer a clash between rulers and their armies but between whole nations.

But, while Grotius considered the entire nation to be the enemy, he kept the medieval distinction between warrior and noncombattant. There were some citizens, he rationalized, who made no “direct contribution” to the war: women, elderly, children, students, priests, and merchants. These should not be attacked.

Though a Christian, Grotius’ many lasting contributions to Just War thinking were admittedly not grounded in his faith.

Grotius had no sense of virtue beyond the natural, and he did not recognize any uniquely religious morality. …Since he had really removed any need for a religious element, Grotius made possible the move to a moral understanding [of war] independent of Christian belief. (2)


  • (1) William Ballis, The Legal Position of War: Changes in Its Practice and Theory from Plato to Vattel (New York: Garland Publishing, 1973), 108

  • (2) Louis A. Manzo, Morailty in War Fighting and Strategic Bombing in World War II (Air Force Historical Foundation, 1992)
  • (3) James Turner Johnson, Ideology, Reason, and the Limitation of War: Religious and Secular Concepts, 1200-1740 (Princeton, N.J.: Princeton University Press, 1975), 214