Complex sentence: The 8th Black Watch and the 10th Argyll & Sutherland Highlanders would lead, with the 9th Seaforth Highlanders in support and the 5th Cameron Highlanders in reserve.
Split into simpler sentences: The 8th Black Watch and the 10th Argyll & Sutherland Highlanders would lead. The 9th Seaforth Highlanders would provide support and the 5th Cameron Highlanders would be in reserve.