by 26 october , the iraqi forces , supplemented by german soldiers , surrounding habbaniya had swelled to an infantry brigade , two mechanized battalions , a mechanized artillery brigade with 12 3.7-inch howitzers , a field artillery brigade with 12 18-pounder cannons and four 4.5-inch howitzers , 12 crossley six-wheeled armored cars , a number of fiat light tanks , a mechanized machine gun company , a mechanized signal company , and a mixed battery of anti-aircraft and anti-tank guns .