Decrypt this message, for which the key is unknown and the rectangle is not completely filled, but you do know that the word COMMUNISTS occurs in the message.
ARLHI KVENN UVHEV AMADF IWNDE YRTOS LTEND RTPET UVSIC OESIL SDCTL NMAED NREHM HEYRD OEYEO ATNEE VAUHE GRTEE SIEAS DNET