If you read about Nomonhan (Khalkhin Gol) from the Japanese side (for example, Coox’s writings) it is pretty clear that the conclusion they drew after the engagement was that they’d better not poke the bear again. Sure they inflicted a lot of casualties on the Russians, but they realized that there was no way they could match Russian armor and logistical support capabilities.
There was a debate in Japan in the Fall of 1941 about striking North while the Russians were engaged with the Germans, but the memory of Nomonhan contributed to their decision to instead go South to scoop up the Euro colonies.
[If you read about Nomonhan (Khalkhin Gol) from the Japanese side (for example, Coox’s writings) it is pretty clear that the conclusion they drew after the engagement was that they’d better not poke the bear again. Sure they inflicted a lot of casualties on the Russians, but they realized that there was no way they could match Russian armor and logistical support capabilities.
There was a debate in Japan in the Fall of 1941 about striking North while the Russians were engaged with the Germans, but the memory of Nomonhan contributed to their decision to instead go South to scoop up the Euro colonies.]
Note that the most compelling reason for not attacking the Russians was the possibility of Russian collapse followed by a German push to the Pacific to gain the rest of Russia’s territories, leaving the Japanese with an aggressive and powerful German presence on their recently-gained Japanese prefectures-in-the-making on the Chinese mainland. A Russian collapse would give the Germans access to oil in the Caucasus, in an environment where Japan was starved for oil, possibly fueling German advances into China at Japanese expense.
Whereas the push south (except for the attack on Pearl Harbor, triggering American retaliation) made a lot of sense, both strategically and tactically. Tactically, except for the Vichy French officials in the region, European colonial efforts were focused on reversing German gains in their metropoles on the Continent. The garrisons in the area were sparsely manned and equipped, with minuscule budgets to match. Strategically, the Dutch East Indies was where Royal Dutch Shell had substantial oil reserves, that could provide the Japanese empire with all it needed if it decided to push further west (e.g. India and the Near East), without having to deal with serious Allied opposition.
Japan’s big mistake was to attack the US. It was perhaps inconceivable to the Japanese High Command that the US would respond with a total mobilization, and a decision to pursue unconditional surrender at tremendous cost as a military objective. Whereas a Russia that could have beaten Japan in 1905, if it had mobilized all its resources, chose not to, ceding land rather than spend money on what it felt to be a peripheral territory of an empire that could be said to have too much land, more than it could defend without the expenditure of exorbitant amounts of manpower and resources.