HHH.....Gee I remember (showing my age now) the days before GPS when you had to navigate by DR and LOP's on ferry flights across the pacific. You could only maintain a heading until you were hopefully in range of a navaid. They were the days when you put the thing on autopilot, set your alarm clock and dozed off for a spell. It took just the odd groan or slight misfire or big pot hole to snap you back to reality though.
I remember the London- Sydney Air Race.....the need for 4 or 5 GPS!!! and they never ALL came back operational!! Those were the days mate.
AS for WW11, I asked the late and great Bobby Gibbs how he became orientated in IMC....to which he replied "Oh that was easy.....when your pens fell out of your pockets you were upside down!! God Love him...a legend.