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Zig-zag convoy plan

Date: 1918
Display dimensions: 590 × 435 mm B Fini
Medium: Paper, ink, pencil
Credit Line: ANMM Collection Gift from Leila Dilley
Classification:Maps, charts and plans
Object Name: Plan
Object No: 00044346

User Terms

    A hand drawn 'zigzag' convoy plan for the HMAT CANBERRA at Mersina, 1918.
    SignificanceThe Signal Log provides an account of the day to day operations of an Australian merchant liner used during wartime. The associated papers provide an insight into the movements of the 'flying convoy', used to move troops and release allied prisoners at Mersina, including 'zigzag' formations and coastal mapping.

    HistoryThe strategy behind the 'zig zag' movement was to make it harder for the German submarines to predict the exact convoy routes. Although such manoeuvring increased transit time of the convoys and “the chances of being sighted are increased and the danger areas increased" ("Analysis of the Advantage of Speed and Changes of Course in Avoiding Attack by Submarine", Navy Department, Office of Naval Intelligence, May 1918), it was generally agreed that its advantages made it an accepted operational practice.
    The 'zig zag' plan shown is based on a timed procedure which would have involved all ships in the convoy changing direction at set times. This zigzagging was carried out according to comprehensive plans which enabled the convoy to zigzag for hours at a time without signals, the courses and the time on each course being designated in the particular plan ordered, all ships' clocks being set exactly the same.
    HMT CANBERRA was requisitioned by the Royal Australian Navy on the 18th of October 1917 in Port Jackson. The signal log provides insight into the day to day operations on board an Australian coastal liner commissioned for use in the First World War. The log spans June to August 1918. In 1918 after the commencement of the German offensive on the Western Front, HMT CANBERRA joined other fast liners forming a "flying convoy" to ship troops from Egypt to France, reinforcing the British presence. From there CANBERRA headed to Mersina releasing British prisoners from the Amara garrison. After taking British prisoners home from India, she returned home with Australian troops and was returned to her owners on the 27th April 1920.

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