From my previous post, I gave out the approximate location of Ma Su: Jieting was a spot connecting An Ding Commandary and Tian Shui Commandary through a mountain range. Tian Shui was under the control of Shu after the surrender of Jiang Wei.
The rebellious Wei army could be ordered to attack Zhang He from the north.
Before the departure ZGL briefed the terrain of Jieting (to Ma Su): there is NO natural barrier around the place. If you were Ma Su, would you deploy your army on the ground, which is to the advantage of Wei army's calvary charge attack, or set up your defense on hill, which increases enemy offensive difficulty? Jieting was relatively far from Chang An. Though Wei captured it then Wei kinda gave it up because it was changed hands for several times between two kingdoms.
Chang An was hell of a place to attack or to siege. It had a formidable castle and endless supplies. ZGL failed to siege Chen Cang though Hao Zhao led only 3,000 men in city during ZGL's 2nd campaign.
Btw what is the link that you listed? I saw all strange symbols once i got in.