Achievements "Hold your Ground" and "Look to your Defenses" Easy Guide

This can be done with any faction which has pike units. My suggestion would be to use Egypt. Egypt start with "Egyptian Pikemen" and these are already recruitable at Alexandria. There is an enemy faction nearby too.

You can do this with a general and 3 pikes but to be safe i like to have 7+ pike units.

You will want to move into the enemies land preferably on the edge of their settlements. If they have better odds of winning they are more likely to attack. Remember to equip fortify stance. This only works if you have 50% of your action points available so be careful of that.

Here is my position vs Cyrenaica. When you end turn, if odds are in their favour they will attack you.

Use the barricades to block 2 of the entrances. Which direction the enemy comes from seems to be completely random so a lot of this is luck. Hopefully they will approach from the 2 barricaded directions. If not, its not the end of the world.

Then cover each entrance with pike units. As in picture.

The next step you will want to put your general behind the wall out of sight.
Best to move the general to the side with the most ranged units. The ranged units will try kill general before the other units, and they will even try kill the general if he is behind a wall. This is a broken R2 mechanic which works with most walls. Archers on the other hand can shoot up and over which is why i suggested Egypt vs Cyrenaica.
Finally, the barricades protect the pike units from arrows, but infantry cant get close to the walls to damage them (and/or the pikes).
Ive used this simple method to take down huge stacks with just 4 units. Although it takes the fun out of it a bit :P