Actually, Ukraine struck first, by attacking the Donbass republics on February 16th, 2022. I know of only a single writer who brought this up, former Swiss Intelligence Officer Jacques Baud, in an article he wrote shortly after Russia's Special Military Operation in Ukraine began. This article can be seen here:
Jacques Baud, a NATO expert, denounces western coverage of the Ukraine invasion.
scheerpost.com
Quoting the most relevant part below:
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In fact, as early as February 16, Joe Biden knows that the Ukrainians began to shell the civilian populations of Donbass, putting Vladimir Putin in front of a difficult choice: to help Donbass militarily and create an international problem or to sit idle and watch Russian speakers from the Donbass being run over.
If he decides to intervene, Vladimir Putin can invoke the international obligation of “ Responsibility To Protect ” (R2P). But he knows that whatever its nature or scale, the intervention will trigger a shower of sanctions. Therefore, whether its intervention is limited to the Donbass or whether it goes further to put pressure on the West for the status of Ukraine, the price to be paid will be the same. This is what he explains in his speech on February 21.
That day, he acceded to the request of the Duma and recognized the independence of the two Republics of Donbass and, in the process, he signed treaties of friendship and assistance with them.
The Ukrainian artillery bombardments on the populations of Donbass continued and, on February 23, the two Republics requested military aid from Russia. On the 24th, Vladimir Putin invokes Article 51 of the United Nations Charter which provides for mutual military assistance within the framework of a defensive alliance.
In order to make the Russian intervention totally illegal in the eyes of the public we deliberately obscure the fact that the war actually started on February 16th. The Ukrainian army was preparing to attack the Donbass as early as 2021, as certain Russian and European intelligence services were well aware… The lawyers will judge.
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Putin himself alluded to what was going on in Donbass on a speech that aired February 24th, 2022, the day Russia started its military operation in Ukraine. Quoting:
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This brings me to the situation in Donbass. We can see that the forces that staged the coup in Ukraine in 2014 have seized power, are keeping it with the help of ornamental election procedures and have abandoned the path of a peaceful conflict settlement. For eight years, for eight endless years we have been doing everything possible to settle the situation by peaceful political means. Everything was in vain.
As I said in my previous address, you cannot look without compassion at what is happening there. It became impossible to tolerate it. We had to stop that atrocity, that genocide of the millions of people who live there and who pinned their hopes on Russia, on all of us. It is their aspirations, the feelings and pain of these people that were the main motivating force behind our decision to recognise the independence of the Donbass people’s republics.
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Full speech:
en.kremlin.ru