SL and SL/MKS Convoy Series



This site is a database of mercantile vessels that sailed in the SL and SL/MKS convoy series. Currently it holds data for 275 convoys in the range SL.1 - SL.178 together with any associated MKS convoys. Please read the notes before using the database. If you have an enquiry or comment concerning a particular OS/KMS or SL/MKS convoy, or a vessel that sailed in them, then please email me and I will do my best to answer you.

For each convoy, vessels are listed in alphabetical order but should you wish to reconstruct the 'Cruising Order' to show the disposition of the ships, you may download a blank form here (print the page in landscape mode and enter the ships' names according to their pendant numbers). For an example of a complete Cruising Order (Form A1), click here.

The SL series of convoy catered for vessels returning to the UK from the South Atlantic commencing from the collection point of Freetown in Sierra Leone. The first SL convoy was in September 1939 and some forty SL convoys had been escorted before the complementary OS series (UK - Freetown) began in July 1941. Initially, the series alternated between fast (SLF) and slow (SL) convoys and from January 1940 (SL.15) the fast convoys would rendezvous with the preceding slow convoy, somewhere within European waters, in order to economise on escort vessels. This practice was in force intermittently until January 1941 (SL.65) when the fast and slow sections were combined. Initially, the fast convoy was designated SLF (SL being SLOW) and later the slow convoy was designated SLS (SL being FAST).

The SL series continued until October, 1942 (SL.125) when it was suspended for five months to free resources for Operation Torch (invasion of North Africa which began on November 8, 1942) and also to avoid crossing the US - UK convoy routes. The series recommenced in March 1943 and in April 1943 it was joined by the MKS series bound for the UK from Gibraltar. While the SL series continued until November, 1944 (SL.178), the OS series continued until May, 1945.

See also the entry for SL convoys and the MKS series in the Arnold Hague database.

Details of the reciprocal OS series of convoy may be found on and in the Arnold Hague database. Russian convoys are listed here.

The author wishes to express thanks to Dominique Lemaire for diligently proofreading these convoy pages.