The Mk. II went into service at the end of 1940 equipped with the Rolls Royce Merlin XII of 1,175 hp. Two main variants were produced, the Mk.IIa with eight machine guns and the Mk.IIb with four machine guns and two 20 mm cannons. The Mk.II's were a transitional aircraft to more powerful forms.
A total of 920 Mk.II's were made. 750 Mk.IIa's and 170 Mk.IIb's
The Mk. I(A) came equipped with 8 Vickers K machine guns, 4 in each wing. A total of 1583 Mk.I's were made.
19 Squadron was issued with half a dozen cannon-armed Spitfires (Mk IB). The cannon's hitting power was recognised but jamming was still a problem and little success was achieved.
The Spitfire Mk.V armament varied from eight machine guns in the MkVa, the four machine guns and two 20mm cannons in the MkVb and the four 20mm cannons in the MkVc. The Vc version used a universal wing capable of fitting all of the armament variations.
Only 94 Mk.Va's were made, 3,923 Mk.Vb's were produced and 2,447 MkVc's were produced.