Board Thread:Warhammer 40k General Discussion/@comment-46.162.84.254-20130704080553/@comment-6078851-20140707163149

plus they need materials for replacing their loses, materials that require processing and manufacturing. as well as needing an energy source to power their military manufacturing, and to power all their technology. tyranids only need a food source, but everything that's organic, and/or mineral (like necrons), is their food source.

against any other opponent necrons would most likely win wars of attrition, but not against tyranids. the plan to end the tyranid threat is easy - destroy any bio-mass source - but implementing that plan pretty much requires that planet after planet is destroyed (actually physically destroyed) because tyranids can, and do, consume almost everything, and that's all they need to keep producing more tyranids - to eat. and though such a plan could, relatively, be easy to do it wont happen because removing a planet from a system can destabalise that system, which in turn can end up destabalising neighbouring systems, which in turn sets up a chain reaction across the galaxy :P