The signing of the Treaty of Paris and the issue of Herat.

On September 3, 1857, one of the most important chapters in the history of Iran-Britain relations unfolded. Following Iran's campaign to Herat during the reign of Naser al-Din Shah Qajar, Britain went to war with Iran in response to this action and occupied parts of the south of the country, including Kharg and Bushehr.

Ultimately, peace negotiations led to the signing of the Treaty of Paris. Based on this agreement, Iran accepted the evacuation of Herat and other Afghan regions and renounced its claims to them.

This treaty effectively marked a turning point in the reduction of Iran's influence in Afghanistan and the increase of British influence in the developments of eastern Iran. Therefore, the Treaty of Paris is considered one of the important agreements in Iran's contemporary history related to border changes and the reduction of Iran's political territory.