Alma 52:26 - 52:30
Alma 52: 26 And thus Moroni had obtained possession of the city Mulek with a part of his army, while he marched with the remainder to meet the Lamanites when they should return from the pursuit of Teancum.
With the city of Mulek now in Nephite hands, Moroni left a few men to maintain the garrison in case the Lamanites returned and marched with his army towards the Lamanites who were pursuing Teancum.
Alma 52: 27 And it came to pass that the Lamanites did pursue Teancum until they came near the city Bountiful, and then they were met by Lehi and a small army, which had been left to protect the city Bountiful.
The Lamanites did chase Teancum until they came into the vicinity of the city of Bountiful. There they met the army of Lehi who had been charged with keeping the city out of Lamanite hands
Alma 52: 28 And now behold, when the chief captains of the Lamanites had beheld Lehi with his army coming against them, they fled in much confusion, lest perhaps they should not obtain the city Mulek before Lehi should overtake them; for they were wearied because of their march, and the men of Lehi were fresh.
The Lamanites now saw the army of Lehi coming to stopped them in their pursuit of Teancum. This brought fear to the Lamanites and they began to flee in confusion back towards the city of Mulek. They were fearful that they would not get back to their stronghold before Lehi and Teancum caught up with them. by this time the Lamanites were very tired because of their strenuous pursuit of Teancum whereas Lehi was fresh and ready to fight.
Alma 52: 29 Now the Lamanites did not know that Moroni had been in their rear with his army; and all they feared was Lehi and his men.
Of course, the Lamanites did not know that Moroni had captured Mulek and all they feared with Lehi and his army.
Alma 52: 30 Now Lehi was not desirous to overtake them till they should meet Moroni and his army.
Now Lehi did not pursue the Lamanites enough to catch them just yet. They wanted them to meet Moroni and his army coming up to their rear first and then Lehi would attack.