Fleet Communications Before Radios

This has been bugging me for a while, and my searching around hasn’t come up with a lot.

Let’s say it’s the early 1860’s in the US. The North has a group of war ships that it is sending to a southern port in order to form a blockade. When the ships leave their home port they know the basic plan, perhaps with a fair amount of detail, such as how the ships will be positioned once they get to where they are going, so there’s probably not a whole lot of intra-fleet communication that needs to happen until they get there. But since they don’t have ship-to-ship radios I assume they use some kind of a semaphore system to communicate between ships that are relatively close to each other (within a few miles) once they are in route to their destination. But how effective is a typical semaphore system during the heat of battle, or during a raging storm, or at night? And wouldn’t the enemy be able to intercept any signals between the ships? They certainly had spyglasses by then. And I realize that ships had lanterns that they could use for signaling, but would they be used during the daytime too?

I suppose if they had to they could send someone in a dingy from one ship to another as a way to relay orders, but what happens when they engage with the enemy, where tactical communications are needed to coordinate the entire fleet at the same time? Is it every ship for themselves, based on a playbook that each ship captain has, or do they use carrier pigeons to spread information? Or is there an easy way to signal each other so that a complicated attack plan can somehow be coordinated in real time? ’

Someone please enlighten me on pre-radio naval ship to ship communications…

In addition to semaphore, ships used flags and colored lights/flares. The Aubrey/Maturin novels dedicate a lot of time to how ships in the early 19th century communicated.

There are several methods of non-radio ship-to-ship communication. Some are in use today (it’s often desirable to maintain radio silence).

Signal flags - have been used for a very long time.
Rockets and flares - rather crude, but useful at night.
Semaphore - simple and surprisingly fast with well-trained signalmen.
Signal lamp - a later development, as this pretty much requires electricity for decent performance.

With all these, a measure of secrecy can be obtained by distributing secret signal books which specify what means what. The fact that they have limited range and in some cases (e.g. signal lamp) are directional can contribute to secrecy.

But there’s no question that all these are crude compared to what’s possible with radio. One consequence was that in battle the ability of commanders to closely direct things wasn’t great, and so the initiative of individual captains was of prime importance. A statement from Nelson before the battle of Trafalgar (which I can’t seem to find just now) said, roughly, “Nothing is sure in a sea fight above all others, but no captain can go far wrong by laying his ship alongside that of an enemy.”

One problem is that during actual battles, visibility was pretty limited due to the smoke from the black powder. So you couldn’t really rely on being able to see signals. You pretty much had to brief your captains beforehand and hope they knew how to follow instructions, something that was not always the case.

They did use smaller ships to relay communications – that was one of the roles of frigates and sloops during fleet engagements.

The Royal Navy had a very elaborate system of flag communication where they could send and receive almost any message they wanted. They used a large code book with hundreds of pre-written phrases which corresponded to numbers like, “attack enemy ship to the west and board it” would be #345 which would be displayed by the 3, 4, 5 flags.

Nelson’s famous message looked like this.


So the answer is “with some sort of signaling capability”, but probably not very effective in real time during a heated battle.

“Heated” is used liberally when talking naval battle.

Sure there are Frantic Moments in trying to reload by the time the ship gets faced side on to an enemy, but there’s a lot of time that the reload is done long before you have a decent shot.

In the Age of Sail, aside from Armada engagements, a typical battle would last several hours. Most of the time was spent trying to get your side facing the other ship without letting them do the same.

In large battles, Captains had a plan to follow and a series of goals. Flag signals could still be used - especially after the advent of spyglasses.

But Captains in those days had to be on-the-fly tacticians who worked well among a fleet of individual thinkers or they didn’t keep command long.

The best book I’ve seen on this topic, indeed a contender for best pop-history I’ve read, is Andrew Gordon’s “The Rules of The Game: Jutland and British Naval Command”. The main topic is leadership, but it talks in some detail about signalling.

But radio is also being de-emphasized now, because it can be overheard by the enemy.

In WWII convoys, they used a lot of signal lamps and even old signal flags, because use of radio, even encoded, could still attract the attention of enemy submarines. And with modern technology, including bombs & missiles that can ‘home in’ on a radio signal, use of radio is often restricted during battles.

Modern techniques (e.g. spread spectrum) make highly secure radio comms rather easy.

Being secure isn’t the problem – cryptography has been around for a long time. The problem is that by broadcasting at all, a ship reveals its presence and location.

Unless it’s a submarine, it does a fairly good job of that simply by being a large object afloat on the ocean. (Yes, there are still times when radio silence is of value.)

But radio detection is a passive technique, you can detect the opposition but they don’t know you have done so. Ships are not easy to find outside of visual range without using radar, but that gives the searching ship or aircraft away.

The question has been mostly answered, but just one additional point:

Early in a naval battle, it isn’t a free-for-all. The standard formations pre aircraft and missiles were based on lines of ships. Mostly, you followed the ship in front of you, who followed the ship in front of them, and typically the command unit was first or second in the line. You could “give orders” just by changing direction.

Nelson won some of his early victories when he wasn’t fleet commander but a subordinate commander. Put simply, he saw an opportunity and, left the main line of battle, dragging all following ships with him into a gap in the enemy formation.

But in the Age of Sail, once a broadside or two was let off, visibility is going to be very limited. Black powder puts off a LOT of smoke. Even when two ships were right next to each other firing away, commanders would sometimes stop firing for a bit just to let the smoke clear enough to be able to see the ship they’d been shooting at.

But (if I understand my Patrick O’Brien correctly), in Age of Sail naval battles, the signaling was mainly used to get the ships lined up and engaged in the battle. Once the broadsides start going off, and the ships go yardarm to yardarm, strategy sort of goes out the window, and things become a series of ship on ship duels until one side is defeated.

Captains necessarily had a good deal of discretion as the vagaries of ship’s rigging, bottom fouling etc. made it impossible to order a common speed or a concerted manoeuvre. When steam came in they gradually realised that this was now possible, provided certain rules were observed.

Here’s more about Nelson’s famous signal to the fleet at Trafalgar in 1805: http://images.google.com/imgres?imgurl=http://newsimg.bbc.co.uk/media/images/40934000/jpg/_40934572_expects203.jpg&imgrefurl=http://news.bbc.co.uk/2/hi/uk_news/4364348.stm&usg=__xZMNGvkH5kU3DbkuXoef0rPbm7U=&h=250&w=203&sz=22&hl=en&start=23&tbnid=QYD4dxuCZ9HEpM:&tbnh=111&tbnw=90&prev=/images%3Fq%3Dnelson%27s%2Bsignal%26gbv%3D2%26ndsp%3D18%26hl%3Den%26sa%3DN%26start%3D18

You can see semaphore signal officers just to the right of the American flag at the stern of Adm. Farragut’s flagship, USS Hartford, in this rather idealized view of the 1864 Battle of Mobile Bay: http://www.corbisimages.com/images/BE001349.jpg?size=67&uid=679511A0-718A-4DE5-84A2-62B16262C414

You can also see a semaphore signalman, in white, in the right background of this painting of Adm. Togo on the quarterdeck of the Mikasa before the 1905 Battle of Tsushima: http://www.reformation.org/e-admiral-togo.jpg