Why Support Equipment is Needed
Support equipment is designed to support offensives or help in defence, hence why it is support equipment. Therefore, support equipment can be the deciding factor in online games particularly if only one player decides to use it.
Using MG Tripods
MGs are great anti-infantry weapons and come with a crew of 2 and a great fire rate. To effectively use an MG you need to choose a postion close to a point of interest, such as a capture zone or strategic position like a hill. When you have found a good location for your MG you can click on the gears symbol (bottom right) and then on the picture of the sandbags to build cover for your MG which is effective against small arms fire, but AT grenades and tanks can easily destroy this protection.
Mortars are designed to be able to arc over defenisve barriers and kill the enemy infantry behind, in this role they are extremely effective, but cannot be used as frontline weaponry. Even though they do come with sandbags for cover i would recommend against using them because it makes it more obvious to the enemy where the mortar is and once found it is an easy target for enemy counter artillery fire or infantry with AT grenades. For these reasons i would also recommend moving the mortar after every few succesful shots.
Using AT Guns
AT guns are usually cheaper than armoured vehicles and are very effective at killing them, however they are vulnrable to enemy HE shells as smaller AT gun crews can be eliminated with a single HE shell. For this reason, as with the mortar, i would recommend against using their sandbags unless no other cover can be found. AT guns should be positioned away from points on hills and other advantageous terrain so that they can overlook the point and kill enemy armour approaching it. The dowside of the AT guns to using tanks to kill enemy armour is that AT guns aren't mobile so enemy mortars or artillery could focus on them.
Artillery is designed to hit enemies from long range to disrupt attacks or destroy static AT guns, they can even be used to target enemy MG tripods that are in hard to reach positions.
The problem with artillery is its cost and that its easy for the enemy to destroy so moving it after every few shots would help keep it alive.
Particularly effective infantry killing artillery are the Nebelwerfers and Katyushas, essentially anything that shoots rockets as they can clear points in seconds in preperation for infantry attacks.
To repair support equipment you can use the spanner button (bottom left).
To move the support equipment quickly you can use light vehicles like armoured cars to tow them by clicking on the chain button (boittom left) when close to the piece of equipment that you want to tow.
To give more ammunition to artillery or MGs you can call out amunition crates, different amunition crates are for different types of equipment. The heavy crates are for artillery and the lighter ones for MGs and infantry.