Buck wrote:
"What methods did they use to do this?"

Terman says on page 1046 of his 1955 "Electronic and Radio Engineering::
"The fact that radio waves propagate away from the transmitter alomg a
great-circle route makes radio direction finding a useful navigational
aid."

Ships and aircraft have been equipped with shielded loop antennas for
direction finding. At frequencies below 500 KHz,bearings can be read
within 1%.

Ionospheric reflection so scrambles polarizations at higher frequencies,
that loop bearings have higher errors.

An Adcock beam antenna can be made to ignore horizontally polarized
waves from a certain direction and respond to only the vertically
polarized waves. It suffers from very low signal pickup as compared with
a loop, but gives accurate bearings at high frequencies over a distance
of 100 miles where a loop would be useless.

In WW-2, aircraft and ships were often equipped with radios such as the
Bendix RA-1B multiband receiver and a loop antenna, or the navy `s
AN//ARC-5 equipment for direction finding.

Best regards, Richard harrison, KB5WZI