Conditions of ground were difficult and varied. On the hard, rocky ground round the Amphitheatre and in the west of the town, the containers of smoke shells bounced a long way and caused an abnormal spread round the point of origin. On soft, boggy or waterlogged ground, as near the railway station, they buried themselves and produced little or no smoke. Monastery Hill was so steep that more than one screen was needed to blind it.

Infantry and tanks agreed that the smoke was helpful in enabling them to approach their objectives, but its value varied according to the time of day. It was usually least effective from about noon to 4 p.m.

Smoke was shown to be a two-edged weapon. The enemy reacted by mortaring and shelling the screened areas; by using Route 6, when blinded to our observers, to bring forward reinforcements and supplies; and by counter-battery fire against guns laying the screen, which, from their regular rate of fire, were comparatively easy for his flash-spotters and sound-rangers to locate.

The area to be screened must be clearly defined and co-ordinated with the operations of flanking formations. On occasions 4 Indian Division found the screen highly inconvenient.

Adequate warning of the period for which smoke will be required must be given to overcome supply difficulties. Unexpectedly long smoke programmes meant that ammunition lorries had to come forward by day and casualties resulted.

The smoke screen should be laid as near to the enemy as possible, to cause him the maximum inconvenience and to deny our troops the minimum of observation. This was not always remembered.

To reduce wear on barrels and damage to recuperator systems, it is essential to rest one gun per troop or arrange for batteries to relieve each other during smoke programmes.

The generators were not able to screen the bridges effectively all day. Their value was principally to reduce the number of hours in the day when the enemy could shell the bridges by observed shooting. The smoke produced by the generators was superior to that of the guns or mortars but the generators were awkward to handle, they absorbed a large number of men in maintaining a screen, they had to be supplemented by artillery smoke when the wind changed and adjustments had to be made, and their emission points were mortared by the enemy, so that the operators needed good cover.