illicit activities. Equipment Weapons Although SOE used some suppressed weapons such as the De Lisle carbine and the Welrod (specifically developed for SOE at Station IX), it took the view that weapons issued to resisters should not require extensive training in their use, or need careful maintenance. The crude and cheap Sten was a favourite. For issue to large forces such as the Yugoslav Partisans, SOE used captured German or Italian weapons. These were available in large quantities after the Tunisian and Sicilian campaigns and the surrender of Italy, and the partisans could acquire ammunition for these weapons (and the Sten) from enemy sources. SOE also adhered to the principle that resistance fighters would be handicapped rather than helped by heavy equipment such as mortars or anti-tank guns. These were awkward to transport, almost impossible to conceal and required skilled and highly trained operators. Later in the war however, when resistance groups staged open rebellions against enemy occupation, some heavy weapons were dispatched, for example to the Maquis du Vercors. Weapons such as the British Army's standard Bren light machine gun were also supplied in such cases. Most SOE agents received training on captured enemy weapons before being sent into enemy-occupied territory. Ordinary SOE agents were also armed with handguns acquired abroad, such as, from 1941, a variety of US pistols, and a large quantity of the Spanish Llama .38 ACP in 1944. Such was SOE's demand for weapons, a consignment of 8,000 Ballester–Molina .45 calibre weapons was purchased from Argentina, apparently with the mediation of the US. SOE agents were issued with the Fairbairn–Sykes fighting knife also issued to Commandos. For specialised operations or use in extreme circumstances, SOE issued small fighting knives which could be concealed in the heel of a hard leather shoe or behind a coat lapel. Given the likely fate of agents captured by the Gestapo, SOE also disguised suicide pills as coat buttons. Sabotage SOE developed a wide range of explosive devices for sabotage, such as limpet mines, shaped charges and time fuses, which were also widely used by commando units. Most of these devices were designed and produced at The Firs. The Time Pencil, invented by Commander A.J.G. Langley, the first commandant of Station XII at Aston was used to give a saboteur time to escape after setting a charge and was far simpler to carry and use than lighted fuses or electrical