Indirect fire by artillery had been around for a long time by the time machine guns became standard issue for the infantry. There were even mortars used in the revolution as well as howitizers, both intended for indirect fire, usually. I still doubt volley fire with rifles was ever used for indirect fire (target unseen) but machine guns were later used for indirect fire (in some armies), expending huge amounts of ammuntion.
While a howitizers are typically employed for indirect fire, training with direct fire on a moving target was still included when I went through artillery training in 1965 at Ft. Sill.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
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