Timothy, you remind me of myself from last IR.
And that gives me an idea...
Edena, I'm going to implement the use of the Trebuchet in my invasion. As a master siege engineer, Gustav will perfect the creation of the weapon, modernized to deliver tons of small lead balls. These lead balls wouldn't be too deadly to troops, had they not been prepared by mass enchantments with fireball and worse. This is our primary siege weapon in use, for the sake of current events.
Figuring that the average Trebuchet we use is 30-60 feet high, with a 25-50 foot arm, we can probably manage a balast of 500 pounds or so, and get a good solid launch of 2000 feet or so. Against 'Hard Targets' like cities and structures, bunkers and dragons, we use 'Solid Shot.' A Solid Shot is a large piece of rounded Mass launched with a contingency Divine Light spell. Against many soft targets, or to deal with air supremecy, we use warped trebuchet arms to fire more 'bowed' arcs of shot at the enemy, in which case we use inch-and-a-half lead and Iron balls for ammunition. These balls are mostly enchanted with Fireball spells that go off at the set distance of striking, creating lines of explosions at any given time. Just one of these should be pretty devastating, so I'm going to believe that I probably have no more than 20 per army, but I will make devastating use of them, and protect them with Iron Knights, Gold Knights, and Summoned Celestials.
Edit: One other idea came to mind. If we are fighting at night, or against anything weak against a Light or Sunlight spell, we will use lead shot once again with multiple Light Spells, thereby acting as a Defender Designator/Blinding Sunlight over a battle-field.
The Reverse is also true, if we need to 'blind' enemies with normal seeing, I'll make heavy use of darkness spells and deeper darkness.
Edit Edit: Ooh, even better idea, I'm also going to make contingincies on 'fireball spread-shot' to instead go off when someone touches them. Instant super-vicious mine-fields wherever we want, whenever we want. This is primarily used to cut enemy movements in half, and cripple their ability to invade.
Edit: Edit: Edit: I expect to be attacked by mages from the sky, so every trebuchet will also make use of a few well-trained anti-mage snipers using long range crossbows and spells to deal with these attackers.