Complex sentence: Of chief concern was finding enough skilled labour, fellers, hauliers and sawyers, and so they requested that a First Battalion of Lumbermen be formed of 1500 Canadian workers to come over to Great Britain to help out.
Split into simpler sentences: Of chief concern was finding enough skilled labour, in particular, fellers, hauliers and sawyers. Therefore they requested that a First Battalion of Lumbermen be formed of 1500 Canadian workers to come over to Great Britain to help out.