Were Stokes mortars assigned to companies by 1917-1918?

Were Stokes mortars already at company level by 1917-1918?

Probably in use with companies by then, but still formally assigned to battalions, whose commanders distributed the available weapons.

Company use and formal assignment are separate issues here. Stokes mortars remained assigned to battalions, whose commanders could distribute available weapons to their companies. The suggestion that they reached companies by 1917-1918 is accepted tentatively. The growing supply of mortars made that distribution possible without proving a formal change in establishment.