My dad and i were debating over the war in Ukraine and he told me that Russia has never attacked, only defend. This seemed highly unreasonable to me but I can’t remember any instance of Russia invading/colonizing another country. (Expect Poland) I know this is a silly question, but as a STEM student i have already forgotten most of my history class from HS.
Just about every country -- especially those older than 80 years -- have attacked another, and plenty have engaged in colonization efforts to various degrees. Russia, with a huge swath of land and a penchant for population policies is no exception. Poland is obviously the main example, but the Caucasus is another famous one, which not only had battles against the Ottoman Empire and Persia, but also against the local peoples with a nasty ethnic cleansing element (hence the reason why the Circassians, despite originating in Circassia north of the Caucasus mostly live in Turkey). This is not to mention Russian invasions of Central Asia or Siberia and what is now the Russian Far East. All of that land at some time had to be conquered, and very few of those inhabitants had any reason to attack Russia -- Russia attacked them. After the conquest of these lands, Russia would colonize them. Frontier garrisons manned with ethnic Russians became towns dominated by ethnic Russians as they were encouraged to move into the newly conquered lands.
This is to be expected though. Russia started out as Muscovy, only one of the many Russian-speaking principalities. Through wars -- both offensive and defensive -- it grew. Although Muscovy lost some wars and was attacked by others, Muscovy attacked just as much as it defended. As Muscovy became Russia, this trend continued. In the medieval and early modern world, this was a common way countries were created. And this is all before the USSR and modern Russia, both of which have done much the same as Imperial Russia.
Another difficulty is that, prior to WW2, who was the attacker and who was defender was not always clear. If A attacked B, then it is easy, but what if A starts to weaken and B attacks into A's territory, now A -- which started attacking -- has become the defender and B -- which started defending -- had become the attacker. Some examples of this would be some of wars against the Swedes, through which Russia gained Finland and the Baltics.
Sources: Charles King, The Ghost of Freedom; Terry Martin, The Affirmative Action Empire.