The Broteforge Empire was on the ropes in space and hadn't even noticed it until it was too late. Luckily, they had some totally unexpected help that was able to change the fate of the battle called the Fourth Wave.
Before the Fourth Wave, there were three major battles and some minor conflicts, and in all of them the Broteforge Empire managed to hold out. However, Broteforge could not consider these battles as victories, because hundreds of people died in each of them. The Broteforge Empire's death toll became even more frightening when the fact that the Melkian Army had only monsters entered the discussion.
There was no doubt about it, Broteforge needed a new strategy. It took a while for them to realize this, but when they did they efficiently began to act.
This change of strategy was masked and seen as a retreat by the Melki Empire.