An unexploded bomb was discovered during an archaeological dig in Fornham St Genevieve this afternoon.
The 29mm Spigot mortar was found by people with metal detectors in a field in the West Suffolk village.
Suffolk Police were called at about 12.50pm and the bomb disposal squad from Colchester arrived at about 2.50pm to carry out a controlled explosion.
The B1116 road was closed for about 15 minutes.
A police spokesman said the bomb was in the middle of a large field and posed no risk to motorists or householders.
Spigot mortars were used in World War Two.