this is how it was prior to machine guns and tanks
Unless OP typo'd the year in the title and this wasn't actually from 1913, Gatling guns had existed for almost half a century and the British Mark I tank was only 3 years away.
To be fair, Europe had spent most of the time the Gatling and Maxim had existed for fighting under the rules of engagement, as the great British Captain Blackadder once noted, that the "prerequisite of a... campaign was that the enemy should under no circumstances carry guns."