Yue Fei got back to his base before he took the time to think about why it was that his opponents, Guan Yu and Meng Tian, didn't react to his obvious provocations to do battle. First off, the 3 bases he just took were definitely no high value targets. This meant that they were some of the more expendable bases out of their whole territory. That is reasonable.
Something else that was possible was that the two of them were targeting something that they felt more important than protecting those three now conquered bases. There might be something that they were targeting, but it shouldn't be anything too important this early in the game.
Yue Fei sent the prisoners that came from the 3 defeated bases to work in manufacturing weapons for Yue Fei's soldiers. They were then promptly moved further inwards towards the base. There was a building where they worked lived and slept. Though not a lot, this first wave of soldiers was the first out of many.
Baron and Yue Fei waited a few more days to gauge Guan Yu, and Meng Tian's reactions. Once they saw that their enemies weren't making a move, they readied multiple armies and set forth to takea huge swath of land and prisoners to work and build even more weapons.
After a month of this type of continuous attacks, Guan Yu and Meng Tian still hadn't shown themselves. This deeply worried Baron and Yue Fei, so after they had decided that sieging bases was no longer they both decided to withdraw back to safe territory as two massive armies to ensure safety.
This instead worked against their favour. On their way back, they encountered a bunch of grouped up mortars constantly firing at them. Every group had 5 mortars, and 10 people. They were tasked with trying to stall out the enemies for as long as possible. This may not have been very effective numbers wise, but the constant threat of death was looming over every soldier that these two had brought with them.
In just the first day of this alone, Baron and Yue Fei had found and destroyed hundreds of these units, but there was always more that showed up. At almost the exact moment, both of them had split up their army into much smaller fragments so as to deal with these nuisances.
They were somewhat successful, these smaller units were still quite big so their presence was still able to be located by the enemy. Another few days of this passed and the enemy switched out their plan to having the mortars firing blindly into the night as well.
This was a difficult position to fight the enemy back, even if they knew where the mortars were, there could already be ambushes waiting for any fools that would try. The two of them stayed their hands until daybreak and continued on like any other. Once the two armies finally made it onto friendly territory, they were quick to find out that they had been played.
In front of them, an army that was close to half their combined numbers were pointing their guns at them. Baron and Yue Fei assessed the situation and thought it was best to just have the majority of the army stay and for a portion to sneak away to get a jump on their enemy.
This was the plan, but while sneaking around to surprise the enemy, Baron caught a wisp of another army coming in to the enemy's aid. Baron quickly returned to Yue Fei and the army he stayed to command.
(BM) "Yue Fei! There is another army that I estimate to be around 50k soldiers that have come to the enemy's aid. If we were even before, it won't be that way for much longer. What do you think our next course of action should be?"
(YF) "Though this is bad news, we shouldn't be panicking just yet. How long do you think it will take them to get here?"
(BM) "At most another day, I could get back so quickly because I only took the fastest men with me. They are coming in from southwest of our current position."
(YF) "Request aid from the other bases then."
(BM) "I don't think that will be a good idea. What if this is what the enemy is planning and as soon as we get reinforcements they send another army in to deal just as many or even more damage that we have done to them?"
(YF) "That's possible. How about we call Meng Yi and ask for his opinion?"
(BM) "That's a good idea. Mess-"
(M) "Sir, Meng Yi on the radio."
(BM) "Meng Yi?"
(MY) "Baron, I know that you guys are in a bit of a pickle, but-"
(BM) "Did you already get word about the other enemy coming from the southwest?"
(MY) "Oh… You won't like the news I have for you then. There is another army coming for you guys to the north. Their estimated time of arrival is another 3 days. We have reason to believe that Guan Yu is personally going to be leading this army that numbers close to 100,00."
(BM) "This isn't good. Is it possible for you to send reinforcements to us?"
(MY) "Yes, that should be a breeze, but the thing with that is that since I am in the middle of a bunch of mountains that could take a while to do. This base is a double edged sword unfortunately."
(YF) "It matters not how long they take. Just get them here as fast as you can manage to do. Our current army is not in the most optimal position to be fighting an army nearly twice their size."
(MY) "Alright, I'll begin immediately."
(BM) "Good, I'll go stall the enemy coming from the southwest for a bit. You focus on the enemy here, Yue Fei."
(YF) "Good luck brother."
(BM) "You as well."
The two of them looked determinately at each other before Baron left with close to 20k soldiers. Intent on stalling them, or even making them retreat, if it was possible.