Who conceived the idea of digging the trench?

When the Confederates besieged Medina, the Prophet (peace and blessings be upon him) consulted his companions on how to defend it. Salman al-Farisi suggested digging a trench, as they used to do so in Persia during sieges. The Prophet (peace and blessings be upon him) and his companions agreed to this plan, which was instrumental in repelling the Confederates and frustrating their efforts.