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 site of a 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 Siege, 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 and returns shows these to be:
- Three 24-pdr carronades
- Eight 32-pdr guns
In the 1859 Orange Bastion still mounted the same eleven guns. a mixture of 32-pdrs and 24-pdrs.
Between November 1866 and May 1877, based on recommendation in the report by Colonel W.F.D. Jervois, a battery of two 10-inch RML guns behind iron shields was built on the bastion. This battery still dominates the Bastion.
By 1886 the armament of the Bastion is shown as having four 32-pdrs on the left flank, three 32-pdrs on the right flank and the two 10-ins RMLs in the centre.
During World War II a Bofors 40 mm gun was installed at Orange Bastion.
The two 10-ins RML guns now mounted behind the Iron Shields at Orange Bastion were moved from King’s Bastion during redevelopment.
The other 10-inch RML gun batteries in Gibraltar are:
- Engineer Battery, 1 gun
- King’s Bastion, 4 guns
- Montague Bastion,3 guns
- Orange Bastion, 2 guns
- Parson’s Lode (Rosia No.9), 3 guns
- South Bastion, 3 guns