The recent Russian invasion of Ukraine was a long time coming and the result of bad decisions when it came to assessing enemy capabilities and the degree of domestic and economic damage attacking a neighbor might bring. The most common causes of wars are territorial disputes and overconfidence by the aggressor. The current war in Ukraine is the result of over a decade of bad decisions by Russian leaders, particularly Vladimir Putin, who has been running Russia for over two decades despite term-limits laws and continued, but futile, popular opposition.
The first actual invasion of Ukraine occurred eight years after five days of popular protests in Ukraine forced a pro-Russia Ukrainian president to flee to Russia. Victor Yanukovych had won the 2010 presidential election because of promises to seek greater economic and diplomatic links with the West. At that point Russia had been interfering in Ukrainian affairs for over a decade in an effort to prevent Ukraine from becoming more Western and less subservient to Russia. Yanukovych was bribed by the Russians to renege on his election promises about closer links with the West. In late 2013 Yanukovych was supposed to sign a political association and free trade agreement with the EU (European Union). To the surprise of the Ukrainians who voted for him, Yanukovych refused to sign the EU agreement and announced he was going to seek closer ties with Russia. This triggered a popular uprising demanding he resign. At first Yanukovych tried using violence to suppress what came to be called the Maidan Revolution. Over a hundred protesters were killed but the number of protesters in Kyiv grew and Yanukovych fled to Russia. The Ukrainian parliament then voted to officially remove Yanukovych from office and an interim president was selected to arrange new elections and sign the EU agreement. Petro Poroshenko was elected president in May 2014
Russia was dismayed by the removal of Yanukovych and turned to more violent solutions to their Ukraine problems. Russia declared that former Ukrainian president Yanukovych was still the legitimate president and had him write a letter requesting Russian military assistance in Crimea, where the new Ukrainian government was threatening to cancel the lease Russia had for their naval base. Russia was providing Yanukovych with sanctuary and protection from prosecution for crimes he is accused of in Ukraine.
Russia was acting on its belief that three Ukrainian provinces, Crimea, Donetsk and Luhansk should be part of Russia because most of the people in those provinces were Russian speakers and could be persuaded to voluntarily join Russia. This turned out to be only partially true. Many of the Russians in Crimea were military personnel and their families, living there because of the continued use of Sevastopol as the Black Sea Fleet headquarters. Russia prepared a surprise operation that involved the 22nd and 45th GRU (Military Intelligence) spetsnaz (special operations) regiments, which were part of the Russian military force but not identified as spetsnaz. There were only a few hundred spetsnaz in Crimea and Ukrainians soon were able to recognize the “little green men” with weapons and lots of attitude wearing uniforms with no insignia. Also identified were recently (after the takeover began) arrived members of the infamous (for brutal but effective special operations in Chechnya) Vostok battalion and an airborne unit (31st Airborne Brigade) that showed up in a lot of tricky situations (Bosnia, Chechnya, Georgia). In other words, what foreign intelligence agencies have come to regard as The Usual Suspects whenever there is an operation using a lot of special operations troops.
In the Crimea all these commando type troops carried out a complex but thorough plan to disrupt Ukrainian control of the Ukrainian military bases in the area and encourage the Ukrainian troops to not resist and eventually to switch sides or peacefully leave. That worked and Russia took back the Crimean Peninsula quickly and with little violence.
Russia already leased the port of Sevastopol for their Black Sea Fleet which had been based there during the Cold War. A 1997 agreement between Russia and Ukraine allowed the Ukrainian fleet to share Sevastopol and the lease was paid in natural gas from a pipeline that passed through Ukraine to East Europe. Russian leaders still believed Crimea was Russian and only became part of Ukraine in 1964 when the dispute over whether Crimea was part of Ukraine or Russia, both parts of the Soviet Union, was settled by the Soviet Union leader Nikita Khrushchev. Since Khrushchev was Ukrainian, he was accused of favoring Ukraine in this matter. Khrushchev was loyal to the Soviet Union, not an independent Ukraine and just wanted the issue settled. This arrangement continued to bother Russian leaders, especially after 1991 when Ukraine became an independent nation.
Encouraged by the success of the Crimea takeover, two months later Russia tried to carry out a similar operation in Donetsk and Luhansk. These two provinces formed Donbas, or the "Donets Basin", an area that was industrialized during the Soviet years with many Russians brought in to augment a Ukrainian workforce.
While some Donbas Russians supported annexation by Russia, via an operation similar to what happened in Crimea, the majority of Donbas Russians favored being Ukrainian. Russia should have known better because Russian minorities in countries that used to be part of the Soviet Union, chose to stay in new nations close to the West and with easy access to the more affluent West European nations. The Baltic States (Lithuania, Latvia and Estonia) wanted to expel their local Russians and it took a while for these ethnic Russians to convince the elected governments that they were loyal citizens of the areas they had long lived in. There was some of this in Ukraine and Russia failed to note that most Russians in Ukraine wanted to remain there as loyal citizens of an independent Ukraine. Despite the fact that many of the Ukrainian troops fighting the Russians in 2022, and earlier, are ethnic Russians, the official Russian attitude was that most Ukrainians, Russian or Ukrainian, oppose Russian interference with Ukraine. This was first demonstrated when the Donbas takeover encountered far more resistance than the one in Crimea. Russia then had no military garrisons in Donbas and only a few Russian GRU operatives there to organize the “spontaneous” demands for independence. Russia’s first response was to send in paramilitary groups and Russian soldiers as “volunteers”. These volunteers were on the Russian payroll.
With the loss of Crimea in February, Ukraine began mobilizing its forces and found that a lot of Ukrainians were volunteering to fight any more Russian attacks. That’s why the takeover in Donbas was halted and despite the Russian volunteers bringing in more troops and heavy weapons, the Ukrainian resistance was formidable and prevailed. A ceasefire was agreed to by the end of 2014 and, despite frequent violations by the Russians, remained in force until February 2022, when Russian troops in Donbas attempted to advance. They made little progress and now the Ukrainians are beginning to counterattack. The Russian forces are demoralized, Russian leaders have run out of ideas and the Ukrainians are not inclined to trust any new Russian peace deals. The Ukrainians want the occupiers out and that seems more likely than Russian holding on to any of Ukraine.