While browsing random articles I found an interesting fact - that USA never formally declared a war in Vietnam. After googling a bit more it turned out that since WW2 USA never formally declared a war - so even first and second wars in Iraq were not formally declared.

That made me wonder - is in modern world sovereign nations technically have a right to officially declare war to other countries or UN prohibits such declarations all together (considers them illegal etc)? And a side question - why USA never formally declared a war against Iraq or Vietnam back in time? What was the legal grounds for military invasion in such case?

  • 1
    Good question. In the US's case, I suspect it has more to do with internal power dynamics and prerogatives of Congress to declare war. In the more general sense, I think the UN's "outlawing" of war except in self-defense has achieved nothing except not calling a war a war. By their nature, nation states and wars both operate somewhat outside what we know as laws, so it sounds rather dumb to try to outlaw them, much as I am fully supportive of a) limiting them b) enforcing binding agreements on the rules of war and c) mechanisms like the International Criminal Court. Commented Jan 22, 2020 at 19:24
  • 1
    I think it's important to note that the US couldn't really care less about what the UN says
    – Alec
    Commented Jan 22, 2020 at 20:15
  • Related if not basically the same question: skeptics.stackexchange.com/questions/45715/… Commented Jan 23, 2020 at 1:14
  • The US did declare war on Japan which brought us into WWII.
    – user29681
    Commented Jan 23, 2020 at 7:03

1 Answer 1


With respect to the Charter of the UN:

Nothing in the present Charter shall impair the inherent right of individual or collective self-defense if an armed attack occurs against a Member of the United Nations...

So, in general, the UN is fine with a nation defending itself. How one defines "self-defense" is, of course, up for debate.

UN involvement in the Korean War was authorized by United Nations Security Council Resolution 84 and United Nations Security Council Resolution 85.

US military involvement in Vietnam (and later further in Laos and Cambodia under Nixon) is rooted in the Gulf of Tonkin Resolution. Essentially, Congress gave President Johnson the power to use military force in Vietnam in order to defend South Vietnam.

The 1991 Gulf War was authorized by the Authorization for Use of Military Force Against Iraq Resolution of 1991

The 2001 invasion of Afghanistan fell under the Authorization for Use of Military Force of 2001, and of Iraq in 2003 with the Authorization for Use of Military Force Against Iraq Resolution of 2002

Further justification for the use of military force is the War Powers Resolution

As for the why, I suspect that you'd have to ask each member of Congress who made each vote, and I imagine that you'd get a variety of responses ranging from:

  • Attempt to limit the president's authority (see how Congress reacted to Nixon expanding the Vietnam war into Cambodia and Laos)
  • The US can use force anyway so it doesn't matter what Congress calls it
  • Ceding war and military conflict powers to the President pushes the blame in that direction as well (e.g. one can imagine a Congressperson telling the press "We gave the President the authority to defend our troops only in Vietnam and he went and invaded Laos! You can't blame us for those negative things")
  • This is totally true, except that, in an ideal world, since you can only make war in self-defense, no war can happen, as the country you are defending against would not itself be able to go to war. Since that ideal world has not happened, we're left with a UN Charter that is routinely ignored. Which is why I was cynical in my comment about "outlawing war". It's like US Prohibition and then everyone happily going on drinking - laws that are routinely ignored are not worth passing as they devalue useful laws. Commented Jan 26, 2020 at 23:06

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .