The January 1917 "Artillery in Offensive Operations" estimated that 18-pounders needed 7.5 shrapnel rounds + 5% HE per yard of front at medium range to cut barbed wire defences, and 20 rounds of HE to destroy trenches in enfilade. The destruction of trenches frontally was generally estimated as requiring twice the enfilade amount. It was estimated that an 18-pounder would fire 200 rounds per day in an "all-out" offensive. It expressed a preference for shrapnel with a long corrector in creeping barrages due to its high number of "man-killing missiles" and its smoke cloud (shrapnel shells were designed to produce a white puff of smoke on bursting, originally as an aid to gunnery spotting). HE was viewed as not providing this necessary visual screen but could be considered for use in creeping and back-barrages in conjunction with smoke shell, but smoke shell was considered "still in its infancy".