In August 1917, the British Royal Flying Corps (RFC) introduced the coordinated large-scale use of single-seat fighter aircraft for low-level ground-attack operations in support of the offensive at Ypres, with Airco DH.5s, which were unsuitable for high-altitude combat, specialising in this role. The tactic proved effective, and was repeated at the Battle of Cambrai in November 1917 by both DH.5s and Sopwith Camels being used in strafing attacks. While the tactic proved successful, losses of the unarmoured fighters proved to be extremely high, reaching up to 30% per day when aircraft were deployed in such attacks. Most losses were due to ground fire, although low-flying aircraft also proved vulnerable to attacks from above by enemy fighters. On the German side, two-seat fighters such as Halberstadt CL.II, originally designed as escort fighters, were also deployed in a similar ground-attack mission, playing an important role in the German counter-offensive at Cambrai. While the CL-type fighters were not armoured, the Germans also introduced more specialised heavily armoured two-seat aircraft such as the Junkers J.I for contact patrol and ground-attack work.
As a result of the high losses sustained during strafing and after seeing the success of the new German types, the RFC instructed the Sopwith Aviation Company to modify a Camel for the close air support mission by fitting downward-firing guns and armour. The modified Camel, known as the "TF.1" (for "trench fighter"), flew on 15 February 1918. Two Lewis guns were fixed to fire downwards and forwards at an angle of 45 degrees and a third gun was mounted on the upper wing. The downward-firing guns proved to be of little use, being almost impossible to aim. The TF.1 did not go into production, but information gained in testing it was used for the Salamander design.
Work on a more advanced armoured fighter, conceived as an armoured version of the Sopwith Snipe, began early in 1918. The forward portion of the fuselage was a 605 lb (275 kg) box of armour plate, forming an integral part of the aircraft structure, protecting the pilot and fuel system, with a 0.315 in (8 mm) front plate, a 0.433 in (11 mm) bottom plate, 0.236 in (6 mm) side plates and rear armour consisting of an 11-gauge and 6-gauge plate separated by an air gap. The rear (unarmoured) section of the fuselage was a generally similar structure to the Snipe’s, but flat sided, to match the forepart. The two-bay wings and tailplane were identical in planform to those of the Snipe, but were strengthened to cope with the extra weight, while the fin and rudder were identical to the Snipe. The new aircraft used the same Bentley BR2 rotary engine as the Snipe, covered by an unarmoured cowling – the foremost armour plate forming the firewall.
Originally an armament of three machine guns was planned, with two Lewis guns firing forwards and downwards through the cockpit floor as in the TF.1, and a forward firing Vickers machine gun. This was changed to a conventional battery of two synchronised Vickers guns in front of the cockpit, as on the Snipe, before the first prototype was complete. The guns were staggered, with the starboard gun mounted a few inches forward of the port one to give more room for ammunition. Four light bombs could also be carried.
The first prototype started flight tests at Brooklands aerodrome on 27 April 1918 and was sent to France for evaluation on 9 May. It was wrecked in a crash on 19 May while being flown by No. 65 Squadron when the pilot had to avoid a tender crossing the aerodrome responding to another crash. While the Salamander was generally considered promising in the ground-attack role, lateral control was recognised as poor. To rectify these problems, the Salamander underwent many of the same modifications to the tail and ailerons as the Snipe.