Hallo, I assume you would like to know the meaning of 'outrange'/'out-range' (these would be two ways of spelling this word correctly) and 'twice' in this context?
To 'outrange' /'out-range' something, means to go/move/shoot further than something else, in this case enemy forces on the ground (soldiers). Here the word twice is used in the sense of 'two times as far', so if we say that the ground forces are 2 km away, then this cannon can hit a target 4 km away, in other words 2 x 2 km. The word 'twice' in this context therefore means 'double the distance'. If you say, for instance, "We had 10 mm of rain yesterday, and today we had twice as much," you would be saying that 20 mm (10 mm x 2) fell today. I hope this is helpful.