You are wrong. By 1982 the momentum of the war had shifted and Iran successfully repelled the massive Iraqi invasion into Iran. Saddam accepted the failure of his invasion and offered peace, but did not offer to pay compensation, so Iran refused and vowed to fight on into Baghdad.
Then the war entered a new phase where Iran counter-invaded into Iraq and Iraq was mostly on the defensive in their territory. That was a clear moment when the perception of the war changed around the world and the West began to fear that Iraq would fall and Iran's revolutionary government would successfully export its Islamic Revolution to Iraq. As a result, they began to resupply Iraq with huge quantities of weapons and even assisted them in the use of chemical weapons (and shielded them from consequences at the UNSC), which hundreds of thousands of Iranians still suffer the effects of today (Iran also had chemical weapons, but Khomeini refused to use them even in response to the Iraqi attacks).
Iraq's use of chemical weapons stalled Iran's offensives into Iraq and the war became a stalemate. The US then shot down an Iranian civil airliner over the Persian Gulf, killing 300 civilians, and refused to apologise (instead awarding the captain of the US ship responsible a medal of honour). The US also directly attacked the Iranian Navy in 1988 (after a US ship struck an Iranian mine in the Persian Gulf, which was aimed at shutting down oil tanker traffic in the Persian Gulf), devastating Iran's small and war-weary navy. After these events, the Iranian leadership realised the West would not stop at anything to prevent an Iranian victory, and they reluctantly agreed to end the war (Khomeini 'drank the chalice of poison').
@Mehdipersian @Hack-Hook feel free to offer any corrections to my brief account of the imposed war above
