Complex sentence: The conditions were so bad that some prisoners thought that conditions in Poland could not be as bad as they were in Vught commenting, Things surely can't be as bad in Poland as they are at Vught.
Split into simpler sentences: The conditions were so bad that some prisoners thought that conditions in Poland could not be as bad as they were in Vught. One prisoner commented, Things surely can't be as bad in Poland as they are at Vught.