Loop 2 of the game is activated only after you have completed all maps (games) in Loop 1 perfectly at the highest difficulty setting (insane mode). If you think you are good after completing Loop 1 at insane level, you will be humbled in Loop 2.
Loop 2 is very challenging, borderlining of being “imbalanced” — like the almost invincible Lu Bu in just the 5th Battle (Battle of Puyang), the flying kite units, the monks who are immune to almost all stratagem and special skills, 3 enemy bosses dashing to your camp in a short straight line and etc. It will take a while to get used to, and in order to complete Loop 2 in “insane” difficulty without the help of money bags, you have to give a lot of thoughts on your party composition, and stratagem to carry with you to battle.
Heroes and equipment that seems useless in Loop 1 can become extremely helpful in Loop 2. Jia Xu, the battle mage, whom most would probably overlook and picked Sima Yi/ Guo Jia instead, is a shining example. In Loop 2 games, the most difficult part is usually the starting, where you have limited gold, and yet in some maps, the starting enemies are aerial or invisible units. Jia Xu is the only mage that could take on the first couple of waves by himself before you have enough gold to plant other heroes.
I spent hours and hours trying to perfect the “insane” levels without resorting to using money bags and camp restoration, and finally I thought this game is turning into hardcore gaming instead of casual gaming and used money bags to breeze through the final 7 or 8 maps… So if you think Loop 2 is difficult and you absolutely must complete all maps in highest difficulty– use money bags, and best yet, use Jia Xu with tons of money bags, and you could have endless “special skills”.