What it is necessary to understand from the beginning is to make use the cannon ONLY for the armored vehicles, NO against the infantry and even against the 4 trucks of transport of troops which will stop at the level of cannon just before the appearance of the tank. For these trucks, use bazookas.
Thus you use the cannon for the armored vehicles (there are 4) and you use your usual weapons to eliminate the infantry.
When a certain number of soldiers is killed, that made to appear the following armored vehicle. Go up fast on the cannon to eliminate it and do not hesitate to save often (no quick save but save by the menu of game).
To summarize, you have 12 shells for the cannon at the beginning of the map. If you make a success of all your shootings on the 4 armored vehicles, it you will remain 8. It is the number which it is necessary to have for to destroy the tank (I made the game in realistic mode, perhaps that it's less in the other modes).
The game not being very well adjusted, the tank shoot you before that you do not see it (!) and sometimes, it eliminates you (!!!). Start again on a previous savegame until you see it. Wait patiently until it is rather close (after the tower of guet), then shoot it blow on blow in the center. You can to eliminate it to 7th blow, but generally to 8th, you destroy it certainly.
Attention, as soon as you see the tank destroyed, go out quickly from the cannon for to make a savegame BEFORE the video !! I say that for the following scene because you will be a gunner on a jeep driven by your companion, and thus you cannot make a savegame and you will be obliged to begin again to destroy the tank to return to the following scene when you will fail (!!!).
And God knows if you will often fail, it is even impossible to arrive there without cheating : locked into the jeep, you follow a ridiculous course and must eliminated a fifty soldiers -I said well 50!!!- without that you can reload in health nor savegame. The best score than I was able to make was to eliminate 34 soldiers while keeping 64 of health -an exploit!-. After that, the jeep stopped stupidly in the middle of the camp and I saw appearing soldiers by group of 3 on my right, on my left, on my front who all shoot me!!! Crazy, completely crazy. Not amazing that Mirage, the devs of Mortyr 2, disappeared from the scene of the video game...
It is pity because in spite these BIG defects, Mortyr 2 left me rather a good recollection.
How I made to pass this scene idiot? Go to in the folder where you installed Mortyr 2, open the file "ar.cfg" (with Notepad).
Approximately in the middle of the file, you see a line "invisible 0". Instead of 0, write 1, thus "invisible 1". Save, close the file, run Mortyr 2 : now, soldiers do not see you any more.
(French, excuse my English)