<a href="https://en.wikipedia.org/wiki/BL_15_inch_Howitzer" class="extiw" title="en:BL 15 inch Howitzer">BL 15 inch howitzer</a> being reloaded in action, 1916, perhaps during the initial bombardment of the Somme June-July 1916. <br>The gun carriage displays its service as: 1915 <a href="https://en.wikipedia.org/wiki/Battle_of_Aubers_Ridge" class="extiw" title="en:Battle of Aubers Ridge">Aubers Ridge</a>, <a href="https://en.wikipedia.org/wiki/Battle_of_Festubert" class="extiw" title="en:Battle of Festubert">Festubert</a>, <a href="https://en.wikipedia.org/wiki/Battle_of_Loos" class="extiw" title="en:Battle of Loos">Loos</a>; 1916: <a href="https://en.wikipedia.org/wiki/Actions_of_the_Bluff,_1916" class="extiw" title="en:Actions of the Bluff, 1916">The "Bluff", Ypres</a>. <br> The original caption states that this is a Canadian howitzer. The battlefield command of these ten 15" guns (manufactured by the <a href="https://en.wikipedia.org/wiki/Coventry_Ordnance_Works" class="extiw" title="en:Coventry Ordnance Works">Coventry Ordnance Works</a>) changed during the war, and several batteries were indeed attached to the <a href="https://en.wikipedia.org/wiki/Canadian_Corps" class="extiw" title="en:Canadian Corps">Canadian Corps</a>: but they were always manned and commanded by marines and officers of the Howitzer Brigade, <a href="https://en.wikipedia.org/wiki/Royal_Marine_Artillery" class="extiw" title="en:Royal Marine Artillery">Royal Marine Artillery</a> (RMA). This is very likely Gun no. 4, Howitzer Brigade, RMA. See also a later photo of the <a href="//commons.wikimedia.org/wiki/File:15_inch_Howitzer_base_riveting_LAC_3194250.jpg" title="File:15 inch Howitzer base riveting LAC 3194250.jpg">same gun under repair in October 1917</a>.<br>Source: General Sir <a href="https://en.wikipedia.org/wiki/Herbert_Blumberg" class="extiw" title="en:Herbert Blumberg">H. E. Blumberg</a> (1927). <i>Britain's Sea Soldiers. A record of the Royal Marines during the war 1914-1919</i>, Chapter 24, "The Howitzer Brigade, Royal Marine Artillery".
Castle, William Ivor (Lieutenant), Canadian official photographer
Library of Congress archive of WWI magazine rotogravure images: <a rel="nofollow" class="external free" href="http://memory.loc.gov/ammem/collections/rotogravures/index.html">http://memory.loc.gov/ammem/collections/rotogravures/index.html</a><br>This image from <i>The War of the Nations</i>, December 31 1919