Guerilla fighters always must develop a clever logistic system to distribute enough food, water, ammunition and weapons in the right location and right time. Cutting their distribution and communication = draining their power until partisans devote much of their time to get food and water instead of fighting.
OK, first Chechen War was complete disaster for Russians, but this came from sending untested battle equipment (T-80s had for example never seen combat and proved to be failure) and also conscripts up against battle-hardened guerillas who had experience before from Karabakh War.
Second Chechen War was totally different. Russia sent professional soliders and used totally different tactics, smashing Chechen guerillas to point where they could not do anything more than harassment and hit-and-run attacks. Also, they wiped out Chechen leadership by assassinations and corruption. Also, by army vs army I had more in mind like WWII (Germany vs USSR for example).