 Complete the following phrase:  A simple field modification, the Flammenwerfer had a portable flamethrower with enough fuel for about 10 seconds of firing at a range of up to 25 m mounted in place of one of the machine guns. The idea came from an experiment during the Spanish Civil War, and was intended to give the Panzer I more firepower against close targets. The conversion was not permanent, and was only reported to be used in the 