The Protocol of Sèvres was an agreement between three countries - Israel, France, and Britain - that was made in 1956. The agreement was about something called the Suez Canal, which is a big waterway that connects Europe and Asia through Egypt.
The Egyptian leader at that time, named Gamal Abdel Nasser, had taken control of the Suez Canal and made it harder for ships from other countries to use it. Israel, France, and Britain were not happy about this because they wanted to use the canal for their ships to travel through.
So, they made a plan to attack Egypt and take over the canal. They arranged that Israel would attack Egypt first and then France and Britain would step in to stop the fighting and take control of the canal.
This plan was outlined in the Protocol of Sèvres, which was a secret agreement between the three countries. However, the plan did not go as they expected, and it caused a lot of problems. Other countries, like the United States and the Soviet Union, got involved, and there was a lot of international disagreement about what should happen.
Eventually, the three countries had to give up their plan, and they withdrew their military forces from Egypt. The Suez Canal was returned to Egyptian control, and a United Nations force was put in place to help keep the peace.
So, the Protocol of Sèvres was an agreement between three countries to try and take control of a big waterway called the Suez Canal, but it didn't work out, and the canal was returned to Egypt.