The Polish Carpathian Brigade arrives at Tobruk in late August 1941

When the Polish Carpathian Brigade was formed in April 1940 in Syria, the Polish government in exile was based in Paris. The brigade gradually grew from Polish soldiers who had escaped internment or captivity and traveled to Syria. After France fell to the Germans and the Vichy government was formed under Marshal Petain, the brigade marched out of Syria and into Palestine. This was in June 1940. Polish soldiers continued to make their way to Palestine to join the brigade. This process continued until Greece was captured by the Germans in April 1941. There ceased to be an easy route out of Eastern Europe to Palestine at that point.
Many of the men who joined the Carpathian Brigade had been officers in the Polish army. A special unit had been formed of some Polish officers in addition to the normal brigade organization. Other officers served in the brigade as non-commissioned officers or as ordinary soldiers. The Carpathian Brigade had the advantage of time to train before they were sent into action at Tobruk. The brigade was actually organized as a brigade group. The brigade group included a cavalry regiment. The brigade commander, Major-General Kopanski, arrived at Tobruk during the night of 25 to 26 August 1941. The general and his staff had lunch with General Morshead and then had a conference. They found that the plan was for them to move into the southern sector and take over from the 20th Brigade (Australian).
The first Polish unit to see action was the field regiment. They were sent to the western sector to relieve the 51st Field Regiment, which was to leave Tobruk. The Polish anti-tank regiment replaced the 24th Anti-Tank Company and the 9th Battery of the 2/3rd Anti-Tank Regiment. Apparently, only the men left and the guns remained in place for the Polish to use. The Polish cavalry regiment replaced the 18th Indian Cavalry Regiment.
The Polish infantry were sent to integrate with the 20th (Australian) Brigade for a week. The Polish would have preferred to be positioned in opposition to Germans, rather than Italian soldiers, but they accepted their assignment. When they listened to news of the Russian front, the Polish disliked both the Germans and Russians, so they were happy to hear of both sets of casualties.
The 20th Brigade was removed during September 3-4 1941. After the 20th Brigade was relieved, that meant that a Tobruk sector was now held by a non-Australian unit. This is based on the account in Vol.III of the Australian Official History.