explosives

explosives were mostly based on TNT (trinitrotoluene) because it melts before it explodes and can therefore be poured into bombs and shells. It is relatively insensitive to shock, a vital factor when firing shells, and cannot be exploded without a detonator. It was used by both sides. When eight parts of TNT were mixed with two parts of ammonium nitrate, which the Axis often did to conserve their stocks of TNT, the result was called amatol.

The synthetic pentaerythritol tetranite, or PETN, was also employed by both sides. Too sensitive to use alone, when mixed 50/50 with TNT it made pentolite which was used extensively in detonators, and hand grenades. Picric acid or lyddite (trinitrophenol), used in the Japanese explosive shimose, and tetryl (trinitrophenylmethylnitramine) were also highly sensitive, the latter having a higher shattering effect (brisance) than TNT. When mixed 70/30 with TNT, tetryl became tetrytol, used by the Allies for demolition and in mines.

Cyclotrimethylene-trinitramine, called cyclonite by the Americans, RDX (Research Department Explosive) by the British, T4 by the Italians, and hexogen by the Germans, was very powerful but was also too sensitive to use alone. The British desensitized it by mixing it with beeswax for shells (Composition A); with TNT and beeswax for bombs (Composition B); and with plasticizing oil for demolition work (Composition C), this last commonly becoming known as plastic explosive, a British invention. The Tizard mission took these formulae to the USA in 1940 where they were subsequently produced in large quantities. However, US ordnance officers were wary of the sensitivity of Composition B, which made it unsuitable for skip bombing.

When, in October 1943, Lord Cherwell (see Lindemann) alerted Churchill to the fact that German bombs were more effective than their Allied counterparts because of the aluminium they contained, Composition B was replaced by titronal, a mixture of TNT and aluminium powder which increased a bomb's power by 50% or more. This realization also led to the production of minol, a mixture of aluminium and amatol, that could devastate an area 80% larger than TNT alone. Minol was also used in depth charges (see anti-submarine weapons) as was torpex, a mixture which contained 40% RDX, 37% TNT, and 18% powdered aluminium which was 50% more powerful than TNT alone.

The power of some explosives was further increased by the shaped, or hollow, charge (see Figures 1 and 2). Although the principle had been known since 1900, it was not until the Second World War that both Germany and the UK developed it simultaneously. Moulding an explosive around a cone concentrated its shock waves and increased its power by up to fifteen times. This also made effective such rocket weapons as the bazooka and panzerfaust but it was also used to increase the potency of plastic explosives, and even semi-armour-piercing bombs. German engineers used hollow charges very effectively when storming the Eben Emael fortress in May 1940. See also engineers, 1(b).