Not always one way, list of notable cases
Radar was initially developed for detection of incoming bombers,
now used in commercial airliners. The microwave oven is also a
consequence of this technology
Public key encryption was claimed to have been developed by the NSA
for military communications. Now strong encryption is in general
use, such as for financial transactions
Jet engines were developed for fighter craft by Britain and Germany
during the Second World War
The Space Race was based on technology, in particular rockets,
designed for nuclear warfare.
The first computers, Colossus and ENIAC were developed for
codebreaking or the calculation of ballastic trajectories
Roman roads were designed for the rapid transport of troops, but
were used by civilians for millennia afterwards
The Global Positioning System (GPS) was developed under the United
States Department of Defense for military navigational purposes.
The system has been released for free civilian use, e.g. in land,
sea and air navigation, cartography and land surveying.
Cyanoacrylate was developed as a replacement for World War II
airplane gun sights, but was too sticky to be useful. It is now
commonly sold as super glue.
Active Sonar was developed during World War 1 to facilitate the
discovery of enemy submarines, which led to medical
ultrasonography.
QUOTE:
Those who beat their swords into plowshares usually end up plowing
for those who kept their swords -Anonymous