A BASTION is a type of relatively low fortification of wood, earth or masonry projecting from a larger defence work, using a rounded, rectangular or angled plan.

The bastion usually serves as a gun platform; it may also house gunpowder or other defensive material. Although claims have been made for Turkish precedence, it is generally conceded that the bastion is an Italian invention.

The word BASTIONE appears in Italian during the late 14th century.

The terms bulwark, baluard, boulevard, tower, platform, fort and bastion were all used at different times to describe projecting artillery positions.

Technical usage from the 16th to the 19th centuries refers to a four-sided work comprising two angled faces joined to the curtain by two shorter flanks.

Earlier usage is imprecise, as is the tendency of modern writers to employ the term for the projecting fortifications of any era.

The inability of medieval fortifications to withstand the effects of gunpowder and cannon in western Europe led to many changes in the design of the architectural defenses of cities.

The first bastions appeared in Italy by around 1450 as modified towers, lower in elevation than the typical medieval tower and with a spreading, scarped base. Early bastions tended to be circular in plan, as at Corinaldo and Morro d’Alba in the Marches. Some early bastions are polygonal in plan, for example the fortress bastion at Fano on the Adriatic. Both types proved suitable for offensive and defensive purposes.

French evidence suggests parallel developments of the bastion. In the late 15th–century fortress of Salses, Roussillon, has steeply scarped circular bastions, and at Fougères, Brittany, there is a tall, projecting gun-tower of about 1480 that resembles a bastion.