There was a lot of development around radio navigation aids in the interwar period. I believe it was even possible to navigate using commercial AM radio broadcasts, as long as the location of the broadcasting station was known. So while the basic method was computing location based on speed and compass bearing from a landmark (possibly accounting for wind drift), I believe a certain level of radio navigation was still going on in cases of adverse weather.
Longer-range bomber flights also did it the same way ocean-faring ships have done in the past few hundred years: they had a roof window for taking celestial fixes with a sextant. Come to think of it, that's how the Apollo capsule also confirmed its location.
Some SLBMs (Submarine Launched Ballistic Missiles) use star sighting to correct their trajectory mid-flight. ICBMs launched from silos know exactly where they're starting from, whereas a submarine is both moving, at different depths and has some error to knowing exactly where it is. Missiles use inertial guidance, so knowing your starting your point is crucial.
How accurate a missile needs to be is a whole other dimension though. If the value of a missile is as retaliation to destroy a city (countervalue) then it can be a large warhead and "miss" by quite a margin but needs some form of credible survivability of an enemy first strike. If the missile is to be used to destroy enemy military installations (counterforce) then it needs to be a lot more accurate but usually the implication is as a first strike so less survivability is required.
When you have nuclear weapons that you can drop from manned aircraft, ICBMs from silos and SLBMs controlled by different military branches there is going to be a lot of politics over what the missile is for, which will determine its required accuracy, which will be a factor on if it needs star sighting.
ICBMs early on applied star tracking to increase precision, starting with pretty simple analog systems (I recall something about shifting a tape with simulated tracker signal to a position matching the launch time) to modern digital map systems.
The Voyager space probes for sure use visual fixes on guide stars, such as Alpha Centauri (and our own Sun?) to ensure correct orientation. Of course, they don't need to navigate much, since given the relative velocities, their thrusters wouldn't make much difference.
And there is a quite-famous scene in Apollo 13 where they literally line-up the Moon itself in the reticule so that their engine burn puts them on exactly the correct trajectory.
I believe several of these were also used by civilian aviation before and after the war
TL;DR: both sides used systems with multiple ground antennas that allowed pilots to essentially triangulate their position or at least know they're in a given lane.
I understand that the germans used radio navigation to guide their nighttime bombers over Britain. Wikipedia suggests that the British quicly countered this.
One thing i find interesting is the fact that by sending beacons ahead of the bombing party, they literally broadcasted their intentions to the enemy but that didn't seem to worry them too much.
There were a great number of inventive aerial navigation systems that predate GPS by many decades. One of my favourite books is Most Secret War[0], a biography by R.V. Jones that details much of the cat and mouse that went into detecting and countering the various systems used by the Axis and the Allies to bomb each other.
Dead Reckoning - Pilots have been using this forever (100+ years). It's just maths: speed + heading + time + wind = position. Still widely used in VFR flying! It was made more accessible with the E6B "computer" from the 1930s, but isn't a computer at all - just a circular slide rule with aviation formulas built in and still used today. Every student pilot still learns this stuff.
Non-Directional Beacon (NDB) / Automatic Direction Finder (ADF) - Introduced 1930s-40s, standard in WWII. Ground station sends signal, aircraft needle points to it. Pretty simple but not super accurate. Still technically operational but barely used anymore. PPLs still learn it in training but honestly who uses this regularly? It's like knowing how to use a fax machine - technically still around but why would you?
Very High Frequency Omnidirectional Range (VOR) & Distance Measuring Equipment (DME) - These work together - VOR gives you direction from a station, DME tells you distance. Developed in the 1940s, and surprisingly still pretty common. Lots of GA pilots use these as primary or backup nav. Created all those "highways in the sky" that formed the airways system. VOR is definitely the most useful of the old-school nav aids, and you'll find these receivers in most cockpits.
Inertial Navigation (INS) - Commercial airliners got these in the 1960s. No external signals needed - just measures acceleration to track position changes from your starting point. Completely self-contained, works anywhere on Earth. Modern versions use laser gyros instead of mechanical parts. The drawback is drift - errors add up over time (1-2 miles per hour). Still used alongside GPS on long-haul flights.
US Postal Arrows: Also, i've not seen them myself - but the US in the 1920s before radio navigation, the US built a system of MASSIVE concrete arrows (up to 70 feet long!) across the country to guide airmail pilots. This was officially called the "Transcontinental Airway System." They were painted bright yellow and paired with beacons/lighthouses for night flying. The system eventually stretched from NY to SF.
Most got dismantled during WWII, but dozens of these concrete arrows still exist today scattered across the western US. It was literally a "follow the yellow brick road" situation for pilots. They'd fly from arrow to arrow during daylight, and at night there were gas powered lights showing them. More info here, https://www.core77.com/posts/25236/what-are-these-giant-conc...
Until you mentioned the E6B I totally had forgotten that half a lifetime ago, as a student pilot I programmed my Radio Shack Pocket PC to do some of the E6B calculations.
It worked, but the usability of the tiny keyboard was crap in a bouncing, vibrating Cessna 152, forcing me to look down at my lap while flying. My instructor once said "you're going to kill yourself using that thing" so I eventually just gave up and bought the electronic E6B.
That's awesome. I found 2 x E6B's in my garage last week after a clean out.
Do you still have the code? I'd love to see how you wrote it.
Try using SkyDemon or ForeFlight on an unmounted mobile phone, checking your way point and dropping it under your seat, whilst flying in congested airspace. It's a mistake you only make once :o
Armed forces have been using variations of grid maps to plan bombardment since time immemorial. Do you really think that before GPS people just walked around lost all of the time?
In addition to what others have said, letting artillery mark targets with colored smoke and simply flying to a grid location and keeping an eye out for these signals also works well.
