would we be "done for" if our gps satellites was destroyed, in a world war?

Loss of GPS would certainly hinder modern troops.

Not just the missiles but everything from artillery ranging and tank movements, your scouts actually knowing where they are, and movements of ships as well as the planes.

Yes their are iniertial navigation systems and ecven the possibility of falling back on map reading.

None of those substitutes are nearly as efficient and in most cases would almost certainly spell disaster.

This is the great trade off with technology.

Technology , when it works gives you an extremely efficient army. It also dramatically increases your reliance on technology from your own country which must be delivered to the war zone.

This also creates a much more brittle military that can be crippled by one component failing.

When you start outsourcing components you become even more vulnerable.

It certainly would not help, but we have fought two world wars and two wars in Asia without the use of GPS, so I think we would be okay.

No. It would certainly hurt us in the short term, but we still train with maps and compasses - so it would only be temporary until we get used to not looking at the machines.

No, the military teaches us to read maps, just in case.

There are regular, AAA style maps available as backup - paper doesn't break.

No, we have back-up systems in case this happens.

Not all our ICBM's have nuclear warheads on them.

Some have satelites on them.

just for that possibility.