Thousands of the Polish army personnel crossed the Polish Romanian border
Here is a nice article throwing some light on their adventures.
ciekawostkihistoryczne.pl/2012/05/31/polak-potrafi-jak-polscy-piloci-uciekali-z-rumunskiej-niewoli/
The first group escaped from the camp in a very simple way. They pulled a large barrel on wheels, normally used for transporting water, out of the shed, loaded their belongings into it and dragged it, shouting in Romanian:
- Apa! [i.e. water - author's note]
The guard, convinced that they were going for water, opened the gate and let the whole group out. Fifteen minutes later, a large group of soldiers marched out of the camp, carrying in their backpacks boards from a building that had been specially dismantled for this purpose. They were led by a colleague dressed in the uniform of a Romanian guard. And the guard let them out without any problems.