The Battle of the Marshes saw an Iraqi defence that had been under continuous strain since 15 February; they were relieved by their use of chemical weapons and defence-in-depth, where they layered defensive lines: even if the Iranians broke through the first line, they were usually unable to break through the second due to exhaustion and heavy losses. They also largely relied on Mi-24 Hind to "hunt" the Iranian troops in the marshes, and at least 20,000 Iranians were killed in the marsh battles. Iran used the marshes as a springboard for future attacks/infiltrations.