Just finished my second game.
First one played as Central Powers in 1914, till the middle of 1917 all Entente countries except UK were beaten and surrendered.
This time I have decided to play as Central Powers in 1918, because I've got like only 2 hours.
Seems like the normal difficulty level is a little bit too easy.
Italy and Arabs surrenders (North Italy, down to Rome and Naples conquered)
Started to regain advantage in the Middle East (One turn needed to retake Jerusalem, Gaza and Aquaba already mine, some fights near to Mosul, but now I can send there 5 infantry units and another 5 garrisons from Greece)
Paris, Nice, Lyon, Dijon taken (together with Verdun, Calais, Rouen), Orlean besieged (should fall in turn or two), Marseille besieged (should fall next turn).
Looks like enemy doesn't have any units to patch the front anymore.
During the whole campaign Entente has got only one possibility to take initiative in western front. In Italy it was slaughter. UK troops in Greece were not reinforcing after 7th or 8th turn.
The only front where I must withdraw my units was Holy Land, but since turn 10 advantage was on my side.
AI has withdrawed from time to time to prevent encirclement, which is good, but usually not the whole front was moving backward, so they were easily loosing even more units.
Once or twice AI put the unit just between four or five of my units. This of course caused this unit to be destroyed, but of course hold my front for that turn. If not this sacrifice Orleans would be already mine, Marseille probably too.
To sum up, artillery barrage (despite that on this scale separate artillery units are very unrealistic) is the key to break the front and run for victory. Be sure to have enough (which means more than enemy) units to patch the front and sacrifce unit from time to time then you can be sure that victory is yours.
Remember that every enemy unit can reinforce only three strength points per turn.
All in all, nice game. I will probably try the harder level.
Below is the situation on western front: