Armia Krajowa soldiers fighting during the Warsaw Uprising, September 1944. One man is armed with Błyskawica machine pistol. 
"Warsaw Uprising was a major World War II operation by the Polish resistance Home Army (Armia Krajowa), to liberate Warsaw from Nazi Germany. The rebellion was timed to coincide with the Soviet Union’s Red Army approaching the eastern suburbs of the city and the retreat of German forces. Controversially, the Soviet advance stopped short, enabling the Germans to regroup and literally demolish the city in crushing the Polish resistance, which fought for 63 days with little outside support.
The uprising began on 1 August 1944, as part of a nationwide plan, Operation Tempest, when the Soviet Army approached Warsaw. The main Polish objectives were to drive the German occupiers from the city and help with the larger fight against Germany and the Axis powers. Secondary political objectives were to liberate Warsaw before the Soviets, to underscore Polishsovereignty by empowering the Polish Underground State before the Soviet-backed Polish Committee of National Liberationcould assume control. Also, short-term causes included the threat of a German round-up of able-bodied Poles, and Moscow radio calling for the Uprising to begin.
Initially, the Poles established control over most of central Warsaw, but the Soviets ignored Polish attempts to establish radio contact and did not advance beyond the city limits. Intense street fighting between the Germans and Poles continued. By 14 September, Polish forces under Soviet high command occupied the east bank of the Wisła River opposite the insurgents’ positions; but only 1,200 men made it across to the west bank, and they were not reinforced by the bulk of the Red Army. This, and the lack of Soviet air support from a base 5 minutes flying time away, led to allegations that Joseph Stalin tactically halted his forces to let the operation fail and allow the Polish nationalists to be crushed.
Winston Churchill pleaded with Stalin and Franklin D. Roosevelt to help Britain’s Polish allies, to no avail. Then, without Sovietair clearance, Churchill sent over 200 low-level supply drops by the Royal Air Force, the South African Air Force and the Polish Air Force under British High Command. Later, after gaining Soviet air clearance, the US Army Air Force sent one high-level mass airdrop as part of Operation Frantic.
Although the exact number of casualties remains unknown, it is estimated that about 16,000 members of the Polish resistance were killed and about 6,000 badly wounded. In addition, between 150,000 and 200,000 Polish civilians died, mostly from mass murders. Jews being harboured by Poles were exposed by German house-to-house clearances and mass evictions of entire neighbourhoods. German casualties totalled over 8,000 soldiers killed and missing, and 9,000 wounded. During the urban combat approximately 25% of Warsaw’s buildings were destroyed. Following the surrender of Polish forces, German troops systematically leveled another 35% of the city block by block. Together with earlier damage suffered in the 1939 invasion of Poland and the Warsaw Ghetto Uprising in 1943, over 85% of the city was destroyed by January 1945, when the Soviets entered the city.” (Source.)
The fact that the Soviet Red Army stopped short of the city, effectively sabotaging the eforts of the uprising, could be explained by the following political conflict between the government of the Soviet Union and the Polish Underground State: 
"Although the Underground State enjoyed broad support throughout much of the war, it was not supported or recognized by the far left (communists). The nationalists from the National Radical Camp Falanga and National Radical Camp ABC opposed the German occupation of Poland and the two movements were quickly replaced by the Konfederacja Narodu, a part of the Polish Underground State which also included most members of the pre-war far-right. Influence of the communists eventually declined amid military reversals (most notably, the failure of the Warsaw Uprising) and the growing hostility of the USSR. The Soviet Union had created an alternative, puppet government in 1944 (the Polish Committee of National Liberation) and ensured it formed the basis of the post-war government in Poland. During the Soviet-backed communist takeover of Poland at the end of the war, many Underground State members were prosecuted as alleged traitors and died in captivity. Abandoned by the Western Allies, finding it impossible to negotiate with the Soviets, and wishing to avoid a civil war, the key institutions of the Underground State dissolved themselves in the first half of 1945." (Source.)

Armia Krajowa soldiers fighting during the Warsaw Uprising, September 1944. One man is armed with Błyskawica machine pistol. 

"Warsaw Uprising was a major World War II operation by the Polish resistance Home Army (Armia Krajowa), to liberate Warsaw from Nazi Germany. The rebellion was timed to coincide with the Soviet Union’s Red Army approaching the eastern suburbs of the city and the retreat of German forces. Controversially, the Soviet advance stopped short, enabling the Germans to regroup and literally demolish the city in crushing the Polish resistance, which fought for 63 days with little outside support.

The uprising began on 1 August 1944, as part of a nationwide plan, Operation Tempest, when the Soviet Army approached Warsaw. The main Polish objectives were to drive the German occupiers from the city and help with the larger fight against Germany and the Axis powers. Secondary political objectives were to liberate Warsaw before the Soviets, to underscore Polishsovereignty by empowering the Polish Underground State before the Soviet-backed Polish Committee of National Liberationcould assume control. Also, short-term causes included the threat of a German round-up of able-bodied Poles, and Moscow radio calling for the Uprising to begin.

Initially, the Poles established control over most of central Warsaw, but the Soviets ignored Polish attempts to establish radio contact and did not advance beyond the city limits. Intense street fighting between the Germans and Poles continued. By 14 September, Polish forces under Soviet high command occupied the east bank of the Wisła River opposite the insurgents’ positions; but only 1,200 men made it across to the west bank, and they were not reinforced by the bulk of the Red Army. This, and the lack of Soviet air support from a base 5 minutes flying time away, led to allegations that Joseph Stalin tactically halted his forces to let the operation fail and allow the Polish nationalists to be crushed.

Winston Churchill pleaded with Stalin and Franklin D. Roosevelt to help Britain’s Polish allies, to no avail. Then, without Sovietair clearance, Churchill sent over 200 low-level supply drops by the Royal Air Force, the South African Air Force and the Polish Air Force under British High Command. Later, after gaining Soviet air clearance, the US Army Air Force sent one high-level mass airdrop as part of Operation Frantic.

Although the exact number of casualties remains unknown, it is estimated that about 16,000 members of the Polish resistance were killed and about 6,000 badly wounded. In addition, between 150,000 and 200,000 Polish civilians died, mostly from mass murders. Jews being harboured by Poles were exposed by German house-to-house clearances and mass evictions of entire neighbourhoods. German casualties totalled over 8,000 soldiers killed and missing, and 9,000 wounded. During the urban combat approximately 25% of Warsaw’s buildings were destroyed. Following the surrender of Polish forces, German troops systematically leveled another 35% of the city block by block. Together with earlier damage suffered in the 1939 invasion of Poland and the Warsaw Ghetto Uprising in 1943, over 85% of the city was destroyed by January 1945, when the Soviets entered the city.” (Source.)

The fact that the Soviet Red Army stopped short of the city, effectively sabotaging the eforts of the uprising, could be explained by the following political conflict between the government of the Soviet Union and the Polish Underground State: 

"Although the Underground State enjoyed broad support throughout much of the war, it was not supported or recognized by the far left (communists). The nationalists from the National Radical Camp Falanga and National Radical Camp ABC opposed the German occupation of Poland and the two movements were quickly replaced by the Konfederacja Narodu, a part of the Polish Underground State which also included most members of the pre-war far-right. Influence of the communists eventually declined amid military reversals (most notably, the failure of the Warsaw Uprising) and the growing hostility of the USSR. The Soviet Union had created an alternative, puppet government in 1944 (the Polish Committee of National Liberation) and ensured it formed the basis of the post-war government in Poland. During the Soviet-backed communist takeover of Poland at the end of the war, many Underground State members were prosecuted as alleged traitors and died in captivity. Abandoned by the Western Allies, finding it impossible to negotiate with the Soviets, and wishing to avoid a civil war, the key institutions of the Underground State dissolved themselves in the first half of 1945." (Source.)