Testudo Formation

In Ancient Roman warfare, the testudo formation was a formation used commonly by the Roman Legions during battles, particularly sieges. Testudo is the Latin word for "tortoise".

In the testudo formation, the men would deploy very densely and position their shields at the sides. The first row of men, possibly excluding the men on the flanks, would hold their shields from about the height of their shins to their eyes, so as to cover the formation's front. The shields would be held in such a way that they presented a shieldwall to all sides. The men in the back ranks would place their shields over their heads to protect the formation from above, balancing the shields on their helmets, overlapping them. If necessary, the legionaries on the sides and rear of the formation could stand sideways or backwards with shields held as the front rows, so as to protect the formation's sides and rear.

Plutarch describes this formation as used by Mark Antony during his invasion of Parthia in 36 BC:

"Then the shield-bearers wheeled round and enclosed the light-armed troops within their ranks, dropped down to one knee, and held their shields out as a defensive barrier. The men behind them held their shields over the heads of the first rank, while the third rank did the same for the second rank. The resulting shape, which is a remarkable sight, looks very like a roof, and is the surest protection against arrows, which just glance off it."