Complex sentence: His battle-weary British troops in worn khaki dress were mistaken at first for Afghan tribesmen by some of the civilians; by contrast the soldiers of the garrison were still splendid in scarlet uniforms with pipeclayed white belts.
Split into simpler sentences: His battle-weary British troops in worn khaki dress were mistaken at first for Afghan tribesmen by some of the civilians. By contrast the soldiers of the garrison were still splendid in scarlet uniforms with pipeclayed white belts.