On 20 July, the UN Security Council passed the U.S.-sponsored Resolution 598, which called for an end to the fighting and a return to pre-war boundaries. This resolution was noted by Iran for being the first resolution to call for a return to the pre-war borders, and setting up a commission to determine the aggressor and compensation.
The attacks on oil tankers continued. Both Iran and Iraq carried out frequent attacks during the first four months of the year. Iran was effectively waging a naval guerilla war with its IRGC navy speedboats, while Iraq attacked with its aircraft. In 1987, Kuwait asked to reflag its tankers to the U.S. flag. They did so in March, and the U.S. Navy began Operation Earnest Will to escort the tankers. The result of Earnest Will would be that while oil tankers shipping Iraqi/Kuwaiti oil were protected, Iranian tankers and neutral tankers shipping to Iran would be unprotected, resulting in both losses for Iran and the undermining of its trade with foreign countries, damaging Iran's economy further.