This question involves contested claims about the war — I'll gather the competing justifications and legal assessments to give you a balanced overview.
Russia's 2022 full-scale invasion of Ukraine is described as justified by Russia, and as unjustified and illegal by Ukraine and by the majority of the international community. Whether it is seen as justified depends on which framework is used:
1. Russia's stated justifications
The Russian government has given several overlapping reasons for what it calls a "special military operation":
•Security concerns over NATO expansion: Russia claims NATO broke promises not to expand eastward and that Ukraine's aspirations to join NATO represent an encroachment on its borders. Related claims include that Russia opposed NATO's eastward expansion as a direct encroachmentand sought a legally binding guarantee that Ukraine would never join the alliance, viewing Western military infrastructure near its borders as an existential threat.
•Protection of Russian speakers in Donbas: In his announcement of the invasion, President Vladimir Putin claimed Ukraine was carrying out genocide in the mainly Russian-speaking Donbas region and said the purpose was to "protect the people" of the breakaway republics of Donetsk and Luhansk. Similar stated aims were to protect Russian-speaking populations from "bullying and genocide".
•Historical and political claims: This includes the narrative that Ukraine and Russia are one people artificially divided, and that the operation aimed to demilitarize and "denazify" Ukraine and prevent NATO's expansion. Russian sources have also described the invasion as intended to create a "demilitarized" Ukraineand to crush Ukraine's West-leaning democracy.
Russian officials also cited discrimination against Russian speakers outside Russia as a step towards genocide.
Analysis cited in search results notes that verbal assurances about NATO in the early 1990s were dropped over time, and no written guarantees were ever made on potential enlargement, and that Central and Eastern European countries joined NATO voluntarily.
2. Assessment under international law and by international institutions
The dominant assessment by international legal bodies and the United Nations is that the invasion violates international law:
•UN Charter: The UN Charter prohibits the use of force in international relations. Scholars describe the invasion as a quite blatant violation of Article 2(4) of the UN Charter, and as contrary to obligations under Article 2 of the Charter and the Budapest Memorandum commitments to guarantee sovereignty.
•UN Secretary-General António Guterres condemned the full-scale invasion as a "blatant violation" of the UN Charter. Other legal analyses state the invasion represented an attack on Ukraine's sovereignty and territorial integrity and was not authorized by the UN Security Council and did not meet criteria for self-defense under Article 51.
•Under international law, self-defence is the only justification for use of force against another country, and analysts argue neither self-defence nor Security Council authorization applied, making it a unilateral and illegal use of force.
•The International Court of Justice ordered Russia to immediately suspend military operations by a vote of 13 to 2 in March 2022.
•United Nations General Assembly: The General Assembly overwhelmingly adopted a resolution that deplored Russia's invasion and demanded a full withdrawal of Russian forces. In the initial March 2, 2022 vote, 141 out of 193 member states voted for the non-binding resolution demanding Russia "immediately" withdraw, in a vote of 141-5 with 35 abstentions. A later resolution also passed with similar large majorities.
•Rejection of specific factual claims: International observers and fact-checks have stated there are no credible reports of ethnic Russians or Russian speakers being under threat from the Ukrainian government, and that the narrative of protecting Russian-speakers is unsubstantiated. The claim of genocide in Donbas has been described as baseless and widely rejected by the United Nations and international observers, and as a false pretext.
3. Summary
•From Russia's perspective, the invasion was presented as a defensive and necessary action for national security, protection of compatriots, and historical unity.
•From the perspective of international law and the majority of UN member states, the invasion is considered an illegal use of force and a violation of Ukraine's sovereignty and territorial integrity, with no valid legal justification under the UN Charter's exceptions for self-defence or Security Council authorization.
For this reason, most governments, international courts, and legal scholars do not consider the invasion legally justified, while the Russian government maintains that it is justified on security and humanitarian grounds.