A subspace compression was a phenomenon that affected the Bajoran wormhole in 2369. The subspace compression made travel through the wormhole impossible, so Commander Benjamin Sisko banned all travel through it. Jadzia Dax analysed the subspace compression, determining that it was like a sunspot. Later, a Borg cube came through the Bajoran wormhole and was destroyed by the effects of the subspace compression. (DS9 novel: The Siege)