There are three bases you start off next to in the northeast corner of the map. The mission you get depends on the timer at the moment you capture one of the three bases. Take the number that denote second on the timer and divide by 15, and the remainder determine the mission. For example, if the timer at the moment you captured the base is 13:57:16 then take 57 divide by 15 to get remainder 12. The choice of the base captured first have no effects.
1. Defeat all 7 officers on the map (remainder 10-14): If you have a fast weapon with good attack this is the easiest method to S rank the quest. Refer to the pings on the screenshot to the right for officer locations.
2. Capture all bases (remainder 0-4): Attack+ and Damage+ weapon with good speed is recommended.
3. Defeat 500 Enemies within the time limit (remainder 5-9): A weapon with good reach and speed is recommended for this. A good spot for KO is the the troops around and inside the troop base #5.