[Public Domain with source.]
History is a fascinating topic.
A few days ago the 80th anniversary of the German invasion of the USSR occurred on June 22nd, a Sunday in 1941.
Some days preceding the anniversary Craig Paul Roberts published an article at Unz Review which asserts that the USSR was planning to invade Germany and that the German attack was pre-emptive. It is an interesting hypothesis. The key source for this article is an earlier one by Laurent Guyénot who in turn is referencing:
a former Soviet military intelligence officer who defected to the West in 1978, and wrote two groundbreaking books under the pseudonym of Viktor Suvorov: first in 1988, Icebreaker: Who Started the Second World War?, and in 2010, after new Russian archives had become accessible, The Chief Culprit: Stalin’s Grand Design to Start World War II.
Essentially the Suvorov thesis is the introduction to Guyénot's article which then continues to present other variants of it and opposition to it. I highly recommend it. The core thesis is that the Molotov-Ribbentrop Pact, a non-aggression pact involving the partitioning of "spheres of influence" in Poland was a devilish trap by Stalin for Germany/Hitler. As a part of that the USSR would provide raw materials to Germany in exchange for technical supplies, which the thesis promotes were used to modernise USSR's military. A point they don’t emphasize is that Hitler actually had to invade Poland to spring this trap.
Presenting a still recent but different interpretation is an article by Dr. Jacques R. Pauwels. His key thesis is that Operation Barbarossa, the German invasion of USSR was the beginning of the end for the Nazi war, particularly focusing on the Nazi defeat on the doorstep of Moscow in December 1941. It is an excellently written and well referenced piece. During it he counters several of the positions advanced by Roberts/Guyénot/Suvorov; that Russia could have attacked Germany at the time (there was a two front war threat from Japan), and that Lend-Lease saved Russia (the benefit of which only came after the successful defense of Moscow).
A point to remember is that one of the root causes, possibly the root cause, of WWII is the carving up of Europe (and the Middle East) and the reparations imposed on Germany at the conclusion of WWI.
The other big factor in all of this are the megalomaniacs in charge.
Sources
World War II Was Stalin’s War, Paul Craig Roberts
Barbarossa: Suvorov's Revisionism Goes Mainstream, Laurent Guyénot
History of World War II: Operation Barbarossa: Myths and Reality, Dr. Jacques R. Pauwels