Except there are going to be less people living in the country...a trend which has continued for the last century.
Agreed. But there will still be far more people than are needed for the (reduced) number of jobs due to the decline of oil.
Yes, civilian vehicles were using wood gas because all the oil was secured for military use.
No, at that point the Germans were running out of oil even for their military. Most of their light vehicles were converted to wood (or coal) gas.
This is what the set-up looks like...it can barely carry its own weight, and not far enough be of any military significance.
Google what the German gasifiers looked like. They mounted on the bumper of the car, or were integrated into it. Here's one German military vehicle that used a gasifier:
View attachment 6034
Right, and those generators draw power from the internal combustion engine, reducing its mileage and adding to the fuel cost of the trip from country to city.
Well, external combustion engines (steam locomotives specifically.) But yes, they will reduce efficiency overall. Many things will be more difficult without cheap supplies of oil.
Ships require a harbour and docks to unload...trucks cant just jump out of the hull across a rocky shoal and land on safe ground.
You keep saying things that make me think you have not read much history. For example, have you ever read about an event called D-day? The allied forces landed tanks, artillery, troop transports etc on beaches that not only did not have docks - they had defenders shooting at them while they did it.
The problem is that land mounted cannons can be much larger with a greater range than anything onboard a sea going vessel, which are also more difficult to aim.
Hmm. Modern sea-going weapons would have no trouble taking out land mounted weapons. For example, modern artillery can fire 20 miles and intelligent munitions can provide pinpoint accuracy. Fire and forget solid fueled rockets can easily take out ground targets 100 miles away.
Keep in mind that people aren't going to forget how to wage war, they are just going to have to do it without oil. A lot will change - but even more won't change. Loss of oil will not result in loss of naval reactors, artillery, rocketry, radar or close in weapons systems (like the Phalanx.)
Any invading armada would be blow out of the water either by land fire or torpedoes launched from nuclear subs.
And the battleships that accompany them will immediately launch their ASROC's. No more submarines, and the next wave lands without a hitch. Unless there's another wave of submarines, of course; the better prepared side will then win.