Shells, incendiary 4.2-inch mortar

In the process of CWS expansion gray areas of mission responsibility were clearly defined, much of this work done under the direction of Maj. Gen. William N. Porter who became Chief, Chemical Warfare Service, in May 1941. This effort to define responsibilities resulted in expanded duties for the CWS, for example, development of a high explosive shell for the 4.2-inch mortar and the acquisition of complete responsibility for the incendiary bomb program. In 1941 the War Department gave the CWS the mission of biological warfare research. 

Army authorized limited procurement of 4.2-inch mortar incendiary shells for field tests. ... 

Gaul and Finkelstein, Incendiaries, pp. 663-75. (2) Lt Oren E. Ross, 4.2-Inch Chemical Mortar Shell, Incendiary, E66R3. TDMR 1218, 5 Mar 46. 

Among the offensive munitions which the CWS procured in World War II were incendiaries of various types, 4.2 inch mortars and shells, flame throwers, smoke, and smoke munitions. 

In 1916 the British introduced a new means of projecting gas, the 4-inch Stokes mortar, developed from the 3-inch version of this weapon, which had been the standard mortar in the British Army. Because of their inability to manufacture gas shells, the British first used the mortar to fire improvised smokes and incendiaries. The Stokes gas shell, or bomb, as the British called it, contained six pounds of agent as compared to three pounds for the British 4.5-inch heavy howitzer shell. 

CWTC hem 1326, Military Requirement and Military Characteristics for Incendiary, 4.2-Inch Chemical Mortar Shell, 24 May 45. (2) Alfred E. Gaul and Leo Finkelstein, Incendiaries, vol. 18, 31 Jan 52, in monograph series. History of Research and Development of the CWS (1 July 1940-31 December 1945), pp. 665-75. 

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