hahaha i found a good strategy if you have enough troops as safety in the back: buy an engineer, have him build the bunker (in the middle of the field but on the bottom of the screen), get a signaller, have the engie build an antenna in the bunker, put them both inside, and taunt until you have enough for an arty strike. use it (hopefully when a new wave spawns) and you will rack up the kills. i was only one german soldier crossing my line away from losing, used this, and i went from 60 kills to 196 before i lost.
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