SOS does not stand for anything. It is not short for "save our souls" or "save our ship". It was chosen because its Morse code, three dots, three dashes and three dots, is easy to send, easy to recognise and almost impossible to confuse with anything else. The words came later, as a way to remember it.
Here it is as a distress call is really sent, in one unbroken run: ...---.... Tap it to hear it.
The signal before SOS: CQD
Radio was new at the start of the twentieth century, and so was the problem of a ship calling for help over it. On 7 January 1904 the Marconi International Marine Communication Company, which supplied operators to many ships, issued Circular 57. From 1 February 1904, it said, ships in distress on its equipment should call -.-. --.- -.., which is CQD.
CQ was already the telegraphers' call to all stations. Adding D, for distress, made "all stations: distress". It did not mean "come quick, danger", another phrase that was fitted to the letters afterwards.
CQD had two weaknesses. It belonged to one company, and its rhythm, long and broken up, did not stand out in a crowded band.
Berlin, 1906
Germany had already adopted its own distress signal in maritime radio rules that took effect on 1 April 1905. In 1906 the first International Radiotelegraph Convention met in Berlin, and its agreement, signed on 3 November 1906, put that signal into the international service regulations. Article XVI read: "Ships in distress shall use the following signal: ...---... repeated at brief intervals."
The convention came into force on 1 July 1908. From that day, SOS was the international distress signal at sea.
Notice what the regulation describes: a pattern of nine sounds, not three letters. Nobody in Berlin was spelling out a word.
Why that pattern
Look at what makes ...---... good for an emergency:
- It is symmetrical. Three short, three long, three short. You cannot get it backwards.
- It is all one kind of sound per group. No mixing of dots and dashes inside a letter, so a frightened or untrained sender is unlikely to garble it.
- It is distinctive. Very little ordinary traffic contains nine signs in that shape, so a listener recognises it instantly, even through noise.
That is the whole reason. The fact that the dots happen to spell S and the dashes O is a coincidence that made the pattern easy to name.
The first SOS calls, and the Titanic
The earliest ship reported to have sent SOS is the Cunard liner Slavonia, wrecked on 10 June 1909. The old habit was slow to die, though. In January 1909 the radio operator Jack Binns had used CQD to summon help when the RMS Republic collided with another liner off Nantucket, and many British operators kept using it.
On the night of 15 April 1912, the Titanic's senior radio operator, Jack Phillips, began by sending CQD. His junior, Harold Bride, suggested SOS, and the two of them mixed the old and new signals through the night. After the Titanic, CQD faded away.
Sent as one signal, not three letters
Normally there is a gap of three units between letters. A real distress call drops those gaps and runs the nine signs together, ...---..., which is why radio operators call SOS a prosign, a procedure signal, rather than a word. Its meaning is closer to "this is the start of a distress message; everyone else keep quiet".
Spelled with gaps, ... --- ..., it is still understood. But if you are sending it with a torch or a horn, the unbroken version is the correct one. You can hear the difference by tapping both examples on this page, one after the other.
Where did "save our souls" come from?
From people looking for a meaning that was never there. A word or phrase invented to fit letters that already existed is called a backronym. "Save our souls" and "save our ship" are the famous ones; they made SOS easier to remember and they spread because they sound right. They are not the origin.
Is SOS still used?
Officially, at sea, no. The Morse distress system was replaced by the satellite-based Global Maritime Distress and Safety System in 1999. When the French Navy stopped using Morse code on 31 January 1997, its final message was "Calling all. This is our last call before our eternal silence."
Unofficially, everywhere. SOS is still recognised as a distress signal sent by any means: a flashing light, a whistle, a mirror, letters stamped in snow. If you ever need it, it will still be understood. Our guide to signalling for help with a flashlight, whistle or mirror covers how to send it well, and the phrases page can flash it on your screen.
SOS and Mayday
Mayday is the spoken equivalent: a voice call, said three times, used on radio telephone. SOS belongs to Morse and to any signal made of on and off. Both mean the same thing: a ship, an aircraft or a person in grave and immediate danger.
In short
SOS is a sound, not an abbreviation. It was adopted in Berlin in 1906, came into force in 1908, saw famous use on the Titanic in 1912, and was retired from official maritime use in 1999. It is still the one Morse signal almost everyone on earth knows, and that is exactly what its designers wanted.