This Bastion was named after William of Orange, (Willem III) who became King of England in 1689. This bastion was built by the British on the original Spanish bastion along the Line Wall Curtain.
In 1758 the main face of the bastion held six guns intended to defend the Old Mole.
During the Great Siege of Gibraltar, the bastion was redesigned and enlarged to become a demi-bastion featuring a retired flank behind an orillon with parapets 12 feet (3.7 m) thick.
In the 1790s, after the conclusion of the Great Sieve, Sir William Green implemented improvement to both Orange and the Montagu Bastions. This included adding counter guards in front of the original walls.
Built by 1823 this counterguard was originally named “Orange Counterguard” but was later renamed as Chatham Counterguard, in honour of the Earl Of Chatham who was the Governor of Gibraltar from 1821.
By 1834 there were eleven guns mounted on Orange Bastion but the caliber is not known. By 1859 Orange Bastion mounted 8 x 32 lbs and 3 x 32 lbs Carronades
By 1886 the armament of the Bastion is shown as 7 x 32lbs Smooth Bore, 2 x 10ins RML and 4 x 32lbs Smooth Bore.
The two heavy RML guns were mounted by 1877 on the face of the bastion with iron shields (Gibraltar Shields) and casemated roofs. Two 10-ins RML guns were mounted.
During World War II a Bofors 40 mm gun was installed at Orange Bastion. Precise location not known at this point.
The two RML guns now mounted at Orange Bastion were moved from King’s Bastion during redevelopment.
It is not known how much of the original RML magazines remain.