、。
What blocked his path was a stone wall under a meter high.
Literal
Going-way [object-を] blocked thing [topic-は], height 1-meter less-than-[足らず] [attributive-の] stone-wall was-[polite-past-でした].
Narrative description. 行く手 ('the way forward, path ahead') is a formal/literary noun. 阻む ('to block, to obstruct, to thwart') is formal. 足らず ('less than, short of') uses the classical negative stem of 足りる ('to be enough') — attached to quantities to mean 'less than, not quite X.' This is a cleft-like structure: ~ものは~でした ('the thing that X was Y'), highlighting the surprising mundane nature of the obstacle.