Short answers, pulled from the story.
The Polish Home Army launched Operation Tempest in Warsaw on the 1st of August 1944. General Tadeusz Bór-Komorowski received authorization from the government-in-exile to begin the uprising whenever he deemed the moment right.
Political goals drove this military operation as much as tactical necessity because the underground state wanted to assert Polish sovereignty before the Soviet-backed Committee of National Liberation took control. The Home Army hoped to liberate the capital before the Red Army could enter and impose a pro-Soviet administration.
Estimates place civilian deaths in Wola alone between 20,000 and 100,000 people during these early days. Perpetrators included Oskar Dirlewanger and Bronislav Kaminski whose forces committed extreme atrocities including gunning down crowds in churchyards and chopping children to pieces.
Stalin ordered Soviet tank units to stop receiving oil from depots shortly after the uprising began on the 1st of August. His advance halted just fifteen kilometers east of Warsaw at Wołomin allowing Germans time to reinforce their positions.
By the 2nd of October Home Army forces surrendered after supplies ran out following sixty-three days of combat. Approximately sixteen thousand resistance members died while six thousand suffered severe wounds and remaining inhabitants were deported to concentration camps once Germans regained control.