in December 1986, with the help of a remote camera, they discovered an intensely radioactive mass more than two meters wide in the basement of Unit Four, which they called "the elephant's foot" for its wrinkled appearance The mass was composed of melted sand, concrete, and a large amount of nuclear fuel that had escaped from the reactor. The concrete beneath the reactor was steaming hot and was breached by now-solidified lava and spectacular unknown crystalline forms termed Chernobyl site. It was concluded that there was no further risk of explosion.
To reduce the spread of radioactive contamination from the wreckage and protect it from weathering, the protective Chernobyl Nuclear Power Plant sarcophagus was built by December 1986.
On 25 December 1986, Iran launched Operation Karbala-4 (Karbala referring to Hussein ibn Ali's Battle of Karbala). According to Iraqi General Ra'ad al-Hamdani, this was a diversionary attack. The Iranians launched an amphibious assault against the Iraqi island of Umm al-Rassas in the Shatt-Al-Arab river, parallel to Khoramshahr. They then set up a pontoon bridge and continued the attack, eventually capturing the island in a costly success but failing to advance further; the Iranians had 60,000 casualties, while the Iraqis 9,500.