With the appartition of a new game mode (that I love to be honest) but horribad tactics used, I think it's time for the basics to be learnt, or taught.
Diclaimer: This guide covers the general ideas. Some of the statements might not be true in situational occasions, but that doesn't make them wrong. This guide covers my opinions on the subject, and therefore might be wrong/biased. I'd be happy to be corrected in a polite fashion and to make modifications to this guide.
Sieges have a defending side and an attacking side. The defenders deploy in areas with high income but can't immediately call for reinforcements, while the attackers deploy in reinforcement objectives with no income. Objectives with average/high value neutral objectives are scattered on the map. The objective are the same as in regular mode: Destroy all commands, kill as many of the opponents with as few losses as possible, or earn a better score than the opponent in a set time.DEFENDER'S basic rules
As a defender, it is important to secure a reinforcement area rather early on in order to take advantage of the higher value of your objectives, but don't send every unit in that quest: You still need to defend your main objectives.
It is also important to deny the attackers any income by sending in ambushes early in neutral objectives you can't defend with strengh.
Artillery has to be placed somewhere where approaches are easy to see.
Controlling every forest with infantry will slow the attacker's progression, and also warn you from which direction the main attack(s) are coming, allowing you to react.ATTACKER'S basic rules
Deny the defender's supply lines, either by placing strong defences in an area, or by placing ambushes in every supply arrow you can't defend.
Don't take too much artillery: If the opponent chooses the objective with artillery in it as a supply line, you won't be able to do anything.
Keep points in reserve: If a defender attacks a supply line with a (non overwhelming) force, you will be able to counter and inflict a severe blow by calling reinforcements in that area.
If you see an attack going your way with a too strong force for you to defend against, retreat, save your high value units, but leave stragglers to cover the retreat and prevent the enemy from securing the area too easily.
Now the basic actions have been cleared, have a little look at this public game:http://wargamereplays.org/index.php?page=replay&id=500
As you can see, the attackers are deploying on three fronts, but still leaving some troops on unused objectives, while the defenders go for a big push top of the map. the attackers try to make an early move, but the north takes heavy casualties due to facing enemies in a 2 or 3 vs 1 situation. As the defenders are making a gigantic push to the top, the players on the right and bottom move directly to the almost unprotected main base. A command vehicle from the player on the right neutralises the high value objective by standing in the area, denying the defenders their income advantage, while troops clear the scarce defences, causing the objective to be captured as command vehicles run around fleeing.
The bulk of the defenders moves back to the main objective, but surrender, realising they will be attacking entrenched and supplied/repaired/refueled opponents in an advantageous position.
So, what were the defender's mistakes?
The attackers went for an all out push to one of the supply lines while only few defences remained in the main base (Hogs that were taken out by AA, artillery, and a group of Leo 2s, with small ATGM teams scattered at random). By focusing on one player, they secured a supply line (not really as there were infantry squads placed to ambush reinforcements) with few casualties, but left their main objective completely vulnerable to most aggressive attackers, by being too far to reinforce or push back an attack. They didn't send any recon prior to attacking to know where attackers were weak, and just counted on overwhelming.
What the attackers did wrong: They all went straight ahead without any recon (I was going to secure the objective on the right until I took the opportunity to attack the main base) causing heavy losses to the top player in his failed attack, while the player in the bottom would have been wiped all the same due to terrain configuration. The player in the top also had quite wrong troops selections (Spetsnaz aren't made to be frontline soldiers for example) and wile he offered a long enough resistance, it could have been slightly better.
[Next: The rest, when I'm in the mood]