Use your 4 Ballistas to take out the trebuchets first. Check the turn counter at the bottom and plan your attack so that you take out a trebuchet before it hits you, if possible.
Fill your army up with 4 Archers and don't do anything with them for their first turn. Second turn they can start moving up to the Infantry, but try to keep out of range from their walk distance.
Once the Trebuchets are taken out, just nuke the infantry by running away from them and shooting at them.
Because you are fighting units that are of higher Age than yours, you will get some losses and the infantry will have a big defense, but as long as you keep your distance, you should be able to take them out.
- L