So far, the Kremlin has been able to finance military spending by selling gold from the Russian National Wealth Fund. Eventually, this fund will run out.

“Forcing the economy to run at the current pace will, however, exacerbate its current problems and only delay the major bust that they will trigger.”

https://www.reuters.com/breakingviews/russian-war-economy-is-overheating-powder-keg-2023-10-25/