London Air Defense in WW1

[Bullethead 12]

I've been looking at trhe P4 screenshots and while they're quite beautiful, I'm a bit concerned about what I assume are supposed to be London's defensive barrage balloons. What I'm seeing looks like something from WW2 during the Battle of Britain, but from what I can tell, in WW1 things were quite different.

 

I've attached a pic from The Sky on Fire, by Raymond H. Fredette, which is about the Gotha and Giant raids on England and the British reaction to them. I highly recommend this book. It's got a wealth of data on the defenses in the London area to stop these raids.

 

Anyway, the P4 screenshots show low-altitude balloon barrages similar to those familiar from WW2 photos. That is, relatively small balloons upholding only their own tether cables, a forest of which from many balloons formed the defense. However, AFAIK, this arrangement wasn't used at London in WW1 (although it was used elsewhere in WW1). This is because these low-level balloons were there to deter low-level attacks, strafing, and divebombing. In WW1, however, London only faced high-level bombing so a different arrangement was required.

 

What they did was to make "balloon aprons" of 3-5 balloons each. As shown in the pic, these balloons were connected by horizontal cables high and low, between which ran long vertical wires. These vertical wires were 1000' long, so give some idea of the huge size of an apron and its balloons. Several such aprons were then arranged in a line, forming a literal wall in the sky across the enemy's line of approach. The balloons usually flew at 7,500-10,000 feet high. Hence the name "barrage", because "barrage" originally meant a barrier to enemy movement. This barrage was strung across the NE corner of Greater London, well inside the primary lines of guns and fighter patrols, as a sort of final line of defense. Their primary purpose was to make the Germans fly over them at a more or less known altitude, which greatly simplified setting AA shell fuzes and directing fighters, plus made the bombing less accurate. So

 

There were never many of these balloon aprons, however. The 1st was made in September 1917, there were 4 by January 1918, and only 10 by the end of the war. The primary defense was guns and aircraft.

 

The 2nd pic shows a map of the whole area covered by the defenses of London in their final form. The darker shaded areas were the 1st built during the latter 1/2 of 1917 and into early 1918, while the lighter shading was installed later in 1918 as guns became availalbe. The system worked as follows:

 

Aircraft were tracked by sound and all aircraft heard within gun areas were assumed to be enemy. Within the gun areas, the guns fired pre-determined curtain barrages across the path of the enemy, shifting to new curtain locations as the bombers advanced. Within the fighter areas were both planes and searchlights. Pilots attempted to find bombers to attack by watching shellbursts, searchlights, and also lighted signal devices on the ground below.