Since 2014, it's clear that Russian troops have invaded Ukrainian territory. Crimea was fully annexed and the Donbass is in a state of perpetual conflict. However, officially speaking, Russia and Ukraine didn't declare war on each other and do maintain diplomatic relations.

What is the reason behind this?

  • 5
    Russia having the largest (or close second largest) nuclear arsenal in the world ? An official war declaration like in the 19th century looks like it would have a bad outcome. May 2, 2017 at 11:32
  • 4
    AFAIK Russian does not admit involvement in Donbass and claims it is only a local pro-Russian insurgency.
    – ohwilleke
    May 2, 2017 at 17:27
  • 15
    I suspect the answer is "Ukraine can't and Russia won't". Who in their right mind would declare war on Russia and get invaded? And why declare war if you'll get what you want without doing so.
    – Bobson
    May 3, 2017 at 4:56
  • 5
    It would be suicidal for Ukraine to even consider such a thing. Russia already control their gas supply. May 6, 2017 at 7:21
  • Related: Right to declare a war in modern time
    – sleske
    May 5, 2022 at 6:57

5 Answers 5


Russia cannot declare war officially:

  • war is expensive
  • it would not have support from Russians. Currently Russia is only "helping" Russian brothers in Ukraine
  • Russia cannot occupy Ukraine. It would have to keep population suppressed by military power. It can occupy only the pro-russian regions which are already out of Ukrainian control.
  • potentially it could trigger WW III (other countries would want to help Ukraine)

In total, military help and support for pro-russian armies is cheaper, and more importantly, gives Russia no responsibility over what the armies do. If the status quo is held for enough time, the pro-russian territories will become part of Russia anyway.

Ukraine cannot declare war officially:

  • it would be a suicide. Its army is no match for Russia.
  • Ukraine cannot currently military defend its own territory. Even small pro-russian armies which are supported by Russia can keep the Ukrainian army at bay. Imagine the whole Russian army fighting.
  • it doesn't have enough proofs that it was Russia who attacked them first. When Crimea was occupied, the Russian soldiers could not be clearly identified as Russians (and Russia was claiming they were Crimeans). If they get the proofs, they get them too late.
  • Ukraine depended on Russian gas. Without it, it could not easily survive winter (exactly for this reason Ukraine finally switched to alternative gas supplies).
  • it would provide Russia with a casus belli. Russia would attack them in turn (in defense), immediately claiming the pro-russian territories as its own.

In summary, Russia did attack Ukraine in a smart way, giving Ukraine no way to attack back.

Ukraine could technically ask UN to interfere but Russia has the right to veto everything therefore there is nothing Ukraine can do.

Currently there is no power in the world that could force Russia to give Crimea back. Russia cannot be fought militarily because that would require the help of at least 2 other great powers (e.g. USA and China), technically triggering WW III with probable nuclear outcome.

  • 3
    -1 for a whole bunch of false claims. For example, Ukraine does not buy gas at Russia since 26/November/2015 — almost 1.5 years by the moment when this answer was written. May 20, 2017 at 0:14
  • 9
    @bytebuster You are right. However, 2 years ago the gas supply was a very important problem. Even in winter 2015/16 Ukraine was still using the gas from Russia (even if originally bought from Slovakia). They had no other gas lines available. Please, tell me which other claims are false.
    – Sulthan
    May 20, 2017 at 15:59
  • 1
    Your post was dated 6 May 2017, and the situation of 4 years ago is not an excuse for false statements about the present. The entire post is based on abstract theories, "common sense", and the author's fantasies about "how it could be generally". Sorry to say, but it also indicates zero knowledge about the topic raised in the original question. The absence of prooflinks is a clear indication where the false claims and abstract theories are. May 20, 2017 at 16:29
  • 5
    @Orangesandlemons I believe he is referring to the Little Green Men
    – Gramatik
    Mar 16, 2018 at 13:46
  • 2
    @DrSheldon Actually I don't think anything is wrong. The army of Ukraine was no match for Russia in 2014. They made a huge step forward.
    – Sulthan
    May 5, 2022 at 7:32

War is the continuation of politics by other means - Carl von Clausewitz.

Practically all state actors in international politics are rational. Certainly there are exceptions, e.g. Nazi Germany after Barbarossa, Fascist Japan after Pearl Harbor, etc. But even North Korea has some rationale for their actions.

Therefore, countries don't fight each other because they want to, but because they see it as a way to "get what they want", i.e. to achieve their political agenda. This is why most wars in human history have been rather limited; total war break out only when both sides know that absolutely no deal can be made.

Now, does this apply to Russia and Ukraine? Certainly not. Russia needs to make a deal some time as the war would make them look bad and likely result in sanctions, plus they just can't (and aren't interested) in occupying, not to mention annexing, Ukraine. Russia's priorities are keeping Ukraine away from the West (or better, pro-Russia), and keeping Crimea, as it is strategically important for Russia. Ukraine's priorities are maintaining its own territorial integrity to the greatest extent, and they'd be more willing than anyone to make a deal (they just don't stand a chance if war escalates).

Since both sides are "gentlemen" and are looking for a deal, why escalate things to the point of official state of war? It's just they couldn't yet reach a deal, but they'd have to arrive at one some time later. War is a very costly way to do politics, and they can't do it for too long, especially if both sides don't have too much money to spare.


The UN Charter prohibits both the threat and the use of force in international conflicts.

Which means that formally declaring war by one country on another is illegal under international law.

That's why virtually nobody declares war anymore. Countries just attack each other, without any formal declarations of war. And they rationalize their violence in some way to make it look consistent with international law.

In USA for example, only the US Congress has the Constitutional right to declare war. And last time this happened was in 1941, after Japan attacked Pearl Harbor.

But USA has been involved in many wars since then anyway. And the US Congress has looked the other way. This is probably because declaring war is now illegal under international law, that USA has agreed to abide by.

  1. Russia does not recognize the current Ukrainian government, claiming "Euromaidan" a coup. Thus, according to Russia's position, current Ukraine has no legal government to be in state of war with.
  2. Considering Donetsk/Lugansk: according to Russia's position, Ukraine experiences an internal civil crisis; the "war" is an illusion created by government-controlled Ukrainian media and Western media, and Russian presence in these states is exclusively based on volunteers. Considering Crimea: according to Russia's position, the Autonomous Republic of Crimea and special municipality of Sevastopol, which used to be in Ukraine, had claimed their independence on referendum, and requested to join Russia the day after.
  3. According to Russia's general position, Russian, Ukrainian and Belarusian nations are one nation, descended from the state of Kievan Rus (The Great Russia, Little/South Russia and White Russia respectively), and state of war would controverse this doctrine of triune. (from interviews of V.Putin)

Ukrainian government directly calls the conflict a war in media, and the question of state of war had been raised for several times already. Although, the government wouldn't want to go for it, since it gives Poroshenko a total control over the state, and the civil rebel might follow.


Neither Ukraine nor Russia want to enter into an official war with each other. Russia does not need to do so. Invading and occupying the whole of Ukraine would be very expensive - too expensive for Russia. It would be an act of aggression - and waging aggressive war is a war crime. It would irreparably damage Russia's relations with the EU and very likely also with most of the rest of the world. Also, Russia does not want to have bad relations with Ukraine, it was forced into the current conflict by the need to protect its vital national interests in the Black Sea. The Donbass and Luhansk insurgencies started on their own and Russia got involved only to protect the Russian-speaking majority in those regions from annihilation by Ukraine's military and paramilitary forces, after the May 3, 2014 massacre in Odessa. Russia would like very much to end the whole situation peacefully and be again on speaking terms with Ukraine and the EU. A major obstacle is, of course, Crimea - Russia will never return it as most Russians (and Crimeans) see Crimea historically as Russian territory. Unless a deal is made on Crimea (most likely where Russia makes major economic concessions to Ukraine in return for Ukraine accepting the permanent loss of Crimea), the political situation in Europe will not improve significantly.

Ukraine, on the other hand, has a good argument for waging war on Russia (loss of Crimea, very likely Russian support for insurgents in Donbass and Luhansk), but sees that it would be folly. Its military is decidedly inferior to Russian military. Also, there are still major parts of Ukraine with significant percentage of Russian-speaking population, which would likely rise in insurgency in case of major Russo-Ukrainian armed conflict. Also, increase in violence would further complicate Ukrainian efforts in EU integration.

With the rising Ukrainian nationalism and the increasingly more and more visible loss of control of the central government over the country (in the recent trade blockade of Donbass by Ukrainian nationalists, president Poroshenko protested the blockade but was unable to force its lifting), it is possible that Ukrainian military will take more forceful action against Donbass and Luhansk, which may force Russia's hand, so not all risk of war is beyond us. I hope it is not necessary to mention what a tragedy that would be for Ukraine and Russia both and that it would leave the political situation in Europe even more strained, possibly for decades. No matter what anybody says, Ukraine and Russia are important parts of Europe and real, all-out war between them is too terrible to contemplate.

  • 4
    " after the May 3, 2014 massacre of pro-Russian activists in Odessa" - could you make your post a bit more neutral? May 5, 2017 at 20:10
  • 2
    A source might make this more believable. I think Russian officials have issued statements reasonably close to most of your claims, so it shouldn't be too hard. The Russian sleeper insurgency in Ukraine is news to me, not that I doubt it, but wouldn't that provide similar grounds for intervention throughout Ukraine as was the case in Crimea?
    – user9389
    May 5, 2017 at 21:34
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    @JonathanReez I've changed the sentence (removed "of pro-russian activists") but 49 dead and over 170 injured civilians qualifies to me as a massacre. I'm not attributing blame, that is for the official investigation to do.
    – Ondrej
    May 6, 2017 at 6:54
  • 4
    Crimea is historically a Russian territory? Not true. Crimea was a part of Russian territory. That gives Russia no right over Crimea though. In the same way they have no right for Alaska. We don't know whether the majority of Crimeans want to be in Ukraine or Russia. The only vote was under Russian occupation, with heavy pro-russian campaign and the results could not be independently verified. Well, and Russia was not forced into the conflict.
    – Sulthan
    May 6, 2017 at 7:29
  • 4
    @JonathanReez, what exactly is "not neutral" about "May 3, 2014 massacre of pro-Russian activists in Odessa". People weren't massacred - i.e. burned alive? They weren't massacred for being pro-Russian? It wasn't on May 3, 2014? It wasn't in Odessa? Aug 9, 2017 at 10:57

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