After two days of cancellations and frustration, the one thousand five hundred and sixty-eight men of the 1st Polish Independent Parachute Brigade Group finally took-off on Thursday 21st September. True to form, however, their departure was not at all a satisfactory affair as they were again delayed by fog and the weather was far from ideal when the first of their one hundred and fourteen C-47's, of the 314th and 315th Troop Carrier Groups, took to the air. Conditions were so poor, in fact, that the aircraft first struggled to gain altitude, then they were ordered to return to their bases because it became clear to those on the ground that, by the time the aircraft returned from the drop, landing conditions would be dangerous. A coded message, ordering the recall, was transmitted to the airborne armada, however the aircraft had been issued with the wrong codes and so it was left to the judgement of individual crews as to whether or not they were indeed being asked to abort. As a result of this confusion, forty-one aircraft, returned to their bases but, due to the poor conditions, most put down at the first airfield they could find; one aircraft became so lost that it landed in Ireland. The five hundred Polish paratroopers in these aircraft endured a further delay of forty-eight hours before, at last, they were dropped near Grave, deep into the 82nd Airborne Division's area, on Saturday 23rd September; the drop zones closer to the Rhine being considered too hazardous at this time.
The majority of the Brigade, one thousand and three men in seventy-three aircraft, flew on, and at approximately 17:00 on Thursday 21st September, the Poles jumped into battle for the first time. Anti-aircraft fire was heavy and five of the C-47's were shot down; all of the paratroopers aboard were able to jump before they crashed, however ten American aircrew lost their lives. The aircraft took evasive action from the fire coming up at them, and in so doing hurled the Polish paratroopers about the cabin and delayed their jump. As the Poles descended they were fired at by German troops on the ground, resulting in five men killed and twenty-five wounded. Despite this, the drop had been successful, if a little untidy, and the Brigade faced no serious opposition in the immediate area.
The paratroopers quickly formed up and went about their assigned tasks. The 3rd Parachute Battalion took up positions along the riverbank, directly to the south of Oosterbeek Church where the Lonsdale Force was based, whilst the 2nd Battalion headed towards the Driel-Heveadorp ferry. The Poles were depending upon this facility to bring them across the River and into the Oosterbeek Perimeter, so naturally Major-General Sosabowski was furious when he discovered that the ferry was no longer in service. He dispatched some of his engineers to the crossing point to attract the attention of those on the opposite bank, unaware that only Germans now occupied this position. This party came under fire when, during the night, they lit a signal flare on the riverbank, but, immediately diving for cover, none of them were hurt. Unknown to both sides, the ferry operator had seen the German capture of Westerbouwing and so had scuttled the ferry to deny them its use.
Major-General Urquhart had witnessed the drop of the Polish Brigade from Oosterbeek and, because he was unable to contact them by radio, he accepted the offer of his Polish Liaison Officer, Captain Zwolanski, to swim the Rhine and inform Sosabowski that his men would attempt to retake both Westerbouwing and the ferry crossing. In addition, he instructed the 1st Airborne's engineers to construct makeshift rafts from Jeep trailers in the hope of bringing the Poles across the River near Oosterbeek Church.
The attempt to capture Westerbouwing failed, and the construction of the boats proved to be a very slow process; by dawn they were still nowhere near ready. Similar efforts to build rafts and locate boats were made on the Polish side of the River, but this also ended in failure. With no hope of transferring any of his men across the Rhine, Sosabowski ordered the Brigade to take up defensive positions around Driel for the night.