The Federal government twice attempted to introduce Conscription, in 1916 and 1917. This was a particularly controversial matter in the country, with labour already short on the farms. Debate around the proposed referendum ran high, the Mercury editor (Lance Thomson) was even challeneged via an anonymous letter about why he had not volunteered for active service. An anti-conscription meeting in the Mannum Institute was attended by 600 people, but 'it is estimated that 80% of those present are of German descent, the majority of whom are in favour of anti-conscription' noted the paper (27 October 1916, p. 4). Such was the level of emotion that the introduction of compulsory enrolment for home service saw an attempted suicide by one young man. Regular reports about local men on active service were interspersed with reports of the Pompoota training farm for returned soldiers. Local enlistees even met up with each other on the other side of the world.

News from the front. Mr C. Perrow of Mannum, received news during the week that his adopted son (Private R. Payne) had been killed in the trenches and sympathy is expressed with the relatives of the brave lad ... Private Jack Dodd, in writing home to Mannum, stated that in walking through the streets of London he collided with the two Mazzarol brothers ... Mr D. Diercks has had letters from his son Oscar ... (15 September 1916, p. 4)

In its early years the Mercury gave wide coverage to news from the myriad of tiny settlements covered by the 'Murray electorate'. Forty different places received news coverage at one time or another. This kind of coverage is common to country newspapers of the period. Local sport was well reported, with hockey and rowing being mentioned regularly, as well as cricket, football, boxing, coursing, billiards and tennis. The last riverboats were still plying the Murray, and the regular Murray Bridge to Mannum trips of the Nellie, Murrundee and Lancashire Lass were advertised in the Mannum mercury. During the First World War the building of the first lock on the Murray, at Blanchetown, began. By 1913 the newspaper had increased from four to five pages and later to six pages, before dropping back to four pages in 1916 with wartime restrictions. Early moving picture shows, early motor cars in the district, the rescue by four year old Lillian Fawcett of a drowning child (15 September 1916, p. 1), the celebration of Empire Day and the annual Mannum Regatta, were all reported in the Mannum mercury. The newspaper closed in March 1917 and was taken over by C.M.R. Dumas of the MountBarker Courier. Many years later, in 1997, the title was revived as the Mannum news page in the MurrayValley Standard.