I believe it was reported that Putin officially declared war on Ukraine, but what’s the point to this “official declaration”? He could have simply invaded without a word, and it would make no difference. Declaring war doesn’t make this any better for the victim. So, what is the point?
This article explains the context, and points out that there hasn’t been an official declaration of war – and that those are pretty rare nowadays.
The military operation in progress is supposedly to help those two disputed regions of Ukraine (Donetsk and Luhansk), which Putin had just “recognised” as independent nations. According to Putin, the Russian people living in these two new republics are suffering “genocide” under the “nazi” regime of the Ukrainian government and thus need military help from Russia, including reprisals against / reconquest of the rest-of-Ukraine. So, no need to declare war : Russia is just helping its two new neighbours defend themselves.
After the Japanese attacked the British in 1941, Churchill formally declared war. When asked why he bothered, he allegedly said, “When you have to kill a man, it costs nothing extra to be polite.”
So that’s one reason.
It meant something in pre-WW2 international law relating to wars, hence the diplomatic formalities. Since then, the development of international law means that armed conflicts are shoehorned into whatever categories permit it as something not-quite-outright-war. And the old diplomatic formalities cease to apply.
In classical public international law (in this field, “classical” means between 1648, when the Westphalian order was established, and roughly WWI), war was considered a permissible tool of politics: State were allowed to use military force against each other, provided that they complied with certain formal rules. The most important of them was the need for a declaration of war. It was this declaration which changed relations between these states from peacetime to wartime conditions, until peace was restored in a peace treaty. This principle was known as the jus ad bellum, the right to war.
Legally, things changed with the Kellogg-Briand Pact of 1928. This was an international treaty in which states renounced the use of war as a tool in politics. This principle was reaffirmed in the UN Charter of 1945, and has also become a rule of customary international law (as the ICJ has held in Nicaragua), which means it is binding even on states that are not a party to these treaties. There are exceptions to the rule, most importantly self-defence, but in the absence of such exceptions the rule in public international law is that the use of force between states is impermissible.
As a result, declarations of war are now meaningless from an international law point of view, because they have lost their previous function of legitimisung military action. They do not normally take place nowadays, although a regime might stilll proclaim them for the show.
Incidentally, another consequence of this development is terminological. In classical international law the word “war” was used for military action that was legitimate under the procedural rules described above, as opposed to military action that had not been properly declared. Since declarations of war don’t have this watershed function anymore, the word “war” has also lost this meaning, and is usually replaced with the term “armed conflict” in contemporary international law. What used to be called the “law of war” is now the “law of armed conflict”. Since jus ad bellum now doesn’t apply anymore, the “law of armed conflict” is largely composed of the jus in bello, the rules that govern how military forces may operate, irrespective of whether the armed conflict as such is legitimate.
For the US, back in college in the 80s, I wrote a lengthy paper on the War Powers Act. Just one in a long list of legislation which was purported to address the use of force, but which has been completely ignored by the executive and legislative branches.
Does the Geneva Convention apply to any armed conflict or just during a declared war?
Armed conflict. “War” is not a meaningful category in today’s public international law anymore.
So, in the Olden Days when proper, formal war was permissible, what word was used for improper military action?
“Gauche.”
“Incursion” or “occupation” if you were staying neutral, “Unprovoked attack” if you disapproved, “Restoring order” if you approved. Or some such.
As ever so often in international law, terminology is not always consistent, because that area of law is not always codified in treaties but based on custom, and different writers use different terms. Grotius, in his international law classic De jure belli ac pacis (English translation, in pdf, here):
Public war, according to the law of nations, is either solemn, that is formal, or
less solemn, that is informal. The name of lawful war is commonly given to what is
here called formal, in the same sense in which a regular will is opposed to a codicil,
or a lawful marriage to the cohabitation of slaves. This opposition by no means
implies that it is not allowed to any man, if he pleases, to make a codicil, or to slaves
to cohabit in matrimony, but only, that, by the civil law, formal wills and solemn
marriages, were attended with peculiar privileges and effects. These observations
were the more necessary ; because many, from a misconception of the word just or
lawful, think that all wars, to which those epithets do not apply, are condemned as
unjust and unlawful. Now to give a war the formality required by the law of nations,
two things are necessary. In the first place it must be made on both sides, by the
sovereign power of the state, and in the next place it must be accompanied with
certain formalities. Both of which are so essential that one is insufficient without the
other.
So for Grotius, it’s apparently not a matter of using a word other than “war” for fighting that does not comply with these formalities, but rather a matter of distinguishing between legitimate and illegitimate wars.
As late as 1907, an attempt was made to codify this in a treaty, the Hague Convention Relative to the Opening of Hostilities. It says in Article 1:
The contracting Powers recognize that hostilities between themselves must not commence without previous and explicit warning, in the form either of a declaration of war, giving reasons, or of an ultimatum with conditional declaration of war.
So they seem to use “hostilities” as a wider term.
As for the Geneva Conventions of 1949, they were actually instrumental in this switch from “war” to “armed conflict”. They share a common Article 2, on which the official commentary of 1952 explains that a declaration of war should not be a prerequisite to the applicability of the rules of armed conflict.