The Dinaminteros were miner-engineers from Catalonia who were proficient in the use of explosives. They were used as assault troops, sappers and anti-tank infantry when subsumed within Catalan formations occasionally.  The Catalans lacked many essential supplies, however, and could not maintain a seperate military identity very long.*
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There is some controversy surrounding the Dinaminteros, concerning how many there were and how they were deployed. Some sources have entire companies of troops armed with dynamite, grenades and other explosives being led by the miner-engineer "Dinamiteros." Other sources mention occasional platoon and squad level groups within companies of riflemen (somewhat as depicted here). Others say they were never organized into any formation as large as a platoon.*
*
In the beginning of the people's uprising against the fascists there might have been large groups of Dinaminteros -- but that type of organization is better left to individual scenarios. In any case, large groups were restricted to Catalonia, and their use in the game should be severely restricted except in custom situations and scenarios.  Perhaps one Peloton of Dinaminteros per 1000 Cost Points (just a suggestion). Grenaderos, on the other hand, may be used at any time in any quantity.