 While Dilkes was moving on Ruffin 's position on Barrosa Ridge , Barnard and the light companies advanced through the woods towards Leval 's division . Unaware of the impending British assault , the French had taken no precautions and were advancing in two columns of march , with no forward line of voltigeurs . The unexpected appearance of British skirmishers caused such confusion that some French regiments , thinking there were cavalry present , formed square . These were prime targets for shrapnel rounds fired by the ten cannon under Major Duncan which , having made rapid progress through the woods , arrived in time to support the skirmish line . As the situation became clearer , the French organised themselves into their customary attacking formation — the ' column of divisions ' — all the time under fire from Barnard 's light companies and Duncan 's artillery . Finally , with the French now in their fighting columns and beginning their advance , Barnard was forced to draw back . Leval 's men then encountered Bushe 's companies of the 20th Portuguese , who supported the light battalion 's retreat and kept the French engaged until Wheatley 's brigade had formed up in line on the edge of the woods . The retreating light companies joined Wheatley 's troops ; Leval 's division of 3 @,@ 800 men was now marching on an Anglo @-@ Portuguese line of 1 @,@ 400 men supported by cannon . 
