That vulnerability is at the root of Russia's entire security philosophy and foreign policy. Russia's European border is entirely open, flat terrain. It's trivially easy to invade Russia, you just walk across the border. What Russia has done to cope with this is to extend the enemy's lines deep into its territory and then cut them off and attrite them. That's a very costly and suboptimal solution, which is why Russia - be it the Tzarist Empire or the Soviet Union - surrounded itself with satellite states. Those satellites are meant to be the battlefield on which to attrite the invader rather than fighting on the Russian homeland.
Nice fan fiction. Did it ever occur to you that you should familiarise yourself with source material first? That is historical data?
Russia has
never had a deliberate doctrine of
using depth for defense. You will not find it in any historical document. The deliberate use of territory as a defensive factor is something that
western commentators erroneously ascribe to Russian strategy. The most famous case being Kutuzov's campaign against Napoleon. That in turn arises spontaneously from the fact that when Russia enters the stage as an European power it already has an extensive territory so
any war that is taking place in Russia will be affected by it. There is no choice of not using territory because the "tyranny of space" is a
fundamental factor, one that determines everything else including your choice of strategy.
Russia doesn't use territory. Territory uses Russia.
If anything the most characteristic and consistent element of Russian strategy is
preemptive warfare. Population size, especially in relation to its neighbours, is the main historical factor determining aggressiveness of states. States with lower populations have much lower aggression - with notable exceptions like Prussia.
Russia's aggressive blundering into Ukraine isn't an exception but the
historical norm.
Russia historically has existed on the outskirts of Europe or "Christendom" as it was referred to at the time. It had a relatively small and dispersed population until the 18th century - at best twice that of Polish Lithuanian Commonwealth, except spread over a much greater area.
This is why from 1400 to 1700 it's the PLC, not Russia, that is the dominant power in the region. At thattime Russia (Muscovy) hardly fights any wars in Europe which is why they can focus on their main threat - Central Asian states - and expands its territory there, as well as commits a genocide of native population which Russian propaganda always omits.
When PLC falters as consequence of Swedish invasion and civil war (aka "Deluge" - part of the religious wars and the most devastating event in Polish history, more so than WW2) Muscovy can use its demographic advantage against both PLC and Sweden during the Great Northern War of 1700-1721 which establishes the Russian Empire. The crucial battle of the war is fought in 1709 at Poltava, but not because Russia smartly uses territory but because Sweden managed to reach that far before it was broken by weather, disease and logistics.
Russian Empire is built in a power vacuum of Europe's wars of religion and only later filled with population growth that far outstrips economic development making Russia the perpetual iron giant with clay feet.
The same thing happened in 1812. Napoleon lost at the very beginning of the campaign in Russia. French victory at battle of Smolensk came
after the greatest loss of force had already occurred due to natural factors. Afterward the campaign was already lost in strategic terms - see the numbers here:
Although technically the entire campaign was ill conceived and driven by Bonaparte's increasingly megalomaniac drive. In any case Kutuzov didn't win anything. He just tagged along. Russian propaganda made him like he did - just like Ukrainian propaganda deals with the current war.
The same thing happened in WW2 when Hitler's forces have beaten a nominally much stronger Soviet army all the way to Moscow to ultimately falter due to natural constraints - distance, exhaustion, weather conditions, numbers and poor preparation. If Hitler wasn't an insane genocidal racist he'd complete what Wilhelm II started: Mitteleuropa.
Territory saves Russia, but
never because Russia skillfully uses it to its advantage. To the contrary: Russians almost always fight badly until forced to run and then the territory saves them when the enemy decides to pursue.
WW1, which Russia has tactically and strategically lost against Germany, was a good demonstration of the preemptive doctrine which involved Russia's aggressive offensive into East Prussia, defeats at battles of Tannenberg and Masurian lakes which were then followed by... another offensive as soon as Russia managed to raise another army. And then again. And again.
Until state collapse.
What happened after WW2 is different. First of all WW2 from Moscow's perspective was the expansion of Great Game i.e. the entry of British and American empires into continental Europe. Therefore the takeover of states east of Germany was seen as a balancing act to Anglo-American take over of states west of Germany.
Don't forget that we live in the future of the past. When the Cold War starts in late 1940s Bretton Woods is split 50/50 between USD and GBP and Britain cooperates with US on nuclear weapons. At the same time Germany is under occupation and France is digging itself out.
What comes of it in 1971 or 1991 is not what both sides imagine in 1947.
Soviet Union needed to secure Germany which required having direct land access to German territory which required occupation of Poland, Czechoslovakia and Hungary. This is why Soviet forces withdrew from those countries when German reunification was agreed and why Soviet forces
never stationed in Romania or Bulgaria.
It wasn't about a buffer but about bridge to Germany - the world's second industrial power during WW2.
This needs to be put in proper context for decisions: during WW2 Germany was more industrialised than Soviet Union, and second only to USA.
Soviet Union, just like Russia before, never needed a "buffer" for defense because its territory amply provided it and it relied on its demographic potential which enabled aggressive strategies with high casualty ratio (and later on nuclear deterrence). In Europe it rarely exceeded the territory of Russian-speaking population and when it did so it was as part of
balancing with other powers like during the Partitions of PLC.
Russian Empire expanded beyond that area only in 19th century due to demographic advantages - see dates, and correct for population density b/c you conquer people, not land.
Expansion into Central Asia and Caucasus was due to rivalry with Britain aka "Great Game".
According to your logic this was necessary as a "protective buffer":
All that nonsense about how Russia needs to defend itself and needs friendly states as a buffer is just propaganda justification for imperialistic wars that Russia wages
right now. It's a deliberate distortion of history to rationalise present action which can't be otherwise rationalised.
It should be obvious what Russia will do if its state survival is threatened.
If historical trends are any indication it will
undergo a revolution, a regime collapse and a civil war with a failed external intervention which will result in re-emergence of new Russian regime - just as it happened in USSR,
despite even large number of nukes.
The problem is already clear when Prigozhin did his coup thing. Russia had no way to respond to sudden aggression deep in its territory. The best they could come up with is destroy the road, fortify Moscow that time. Hopefully Russian take this lesson to heart this time.
That's because Prigozhin commanded a force that was part of the Russian military, greatly expanded for the purpose of facilitating the invasion of Ukraine without conscription. Prigozhin's coup occurs in June of 2023 which is no accident. It is when the initial period for establishing forces of reservists and conscripts from late-2022 mobilisation (legally: in newly annexed Russian territory) was coming to an end. Wagner was the interim measure before mobilisation plugged the gap between requirements and resources provided by the invasion plan. If Prigozhin wanted to make his move it was the last moment. He did, and he failed because he was never given sufficient forces to become a viable threat. Yes, the coup was a mess because Russian state is a mess.
Also he wasn't stopped by the military not so much because Russia couldn't do it, but because the military, and GRU especially, wanted to use Wagner (an FSB creation) against security clique ruling in Moscow. So they said "very busy, can't help" and stood by as FSB clique shot itself in the foot again (first in 2022) and Wagner was integrated into the army.
