EMP (electromagnetic pulse) warfare could be the thing that brings about the sticks and stones that Albert Einstien predicted World War Four would be fought with. EMP destroys all electronics within its effective radius, and large scale EMP warfare or terrorist attack could lead to the destruction of civilian electronics in a large area. Unlike many military systems, most civilian systems aren't hardened against EMP, and while the internet is hardened, accessing the internet without a computer is pretty dang hard. Popular literature has already envisioned something similar - In the book One Second After,by William R. Forstchen, terrorists launch an EMP assault on the US. EMP is deadly because of how electronics have been integrated into society. It is theoretically possible to survive in the US without the use of personal electronics, but with the exception of those who live in handbuilt shelter and hunt with a bow, everyone uses electronics at second hand. Even excluding the manufacturing process, electronics are a vital part of the US economy. Trucks use electronics to start their engines, moving supplies and consumer goods across the US. People use cell phones to communicate.
EMP weapons come in three forms. The first of these forms is Nuclear EMP. All nukes produce EMP, but when a nuke is exploded in space, the EMP produced is many times that of a nuclear explosion in air.
Other EMP weapons, generally involving High Power Microwaves (HPMs), or flux compression generator bombs (FCGs) also pose a threat, but their "footprint" is much smaller than that of nuclear EMP.
Will EMP cause Einstien's sticks and stones?
How Stuff Works, "How E-Bombs Work"
"The Blackout Bomb" by John Lewallen