[Saurreg]

I for one tend to think of the phalanx contigent as a unit of Dunlendings specially organized, equiped and trained to repel cavalry.

If memory serves (it seldom does now), the Dunlending has had contact with the Rohirrim and relationships between both people were a wee bit hostile. Thus if Saruman needed a human look in his army, the Dunlendings would be the best candidates. Or that was needed for the walled up tide of bad feelings to flow was a little push and Saruman could have done that. As Erkenbrand explained to the captives at the foot of Helmsdeep, they were misled by Saruman and I dare say it was due to their prolonged bias and hatred to the horse-tamers.

As for the equipment and tactics, both could have been bestowed upon by Saruman or not. Stephen Dando-Collins stated in his book Caesar's Legion" that when the Helvetii attacked, they made use of the Greek phalanx. A classic case of monkey see, monkey do. The dunlendings could also have done so, either from the memories of some elders who had seen phalanx in action or have heard stories of how moving pikes mowed down everything before it. It doesn't take a rocket scientist to figure out that the longer the pike, the lesser chance a horseman can get to you and that if every pikemen cluster together and point their pike tips in the same direction and advance, the chances of sucess are much higher for say a lone naked fanatic with an axe.

That said, I will not discount the fact Saruman might have his orcs round up a motley crue and have them taken to him. He'll look at the bunch, stroke his beard and say,

"Alright then! You see those big sticks laying on the ground there? Yes, those. Now I want every single one of you to pick up a stick. No! Not those twigs at your feet! I meant THOSE sticks over there! Yes, good... Now I want you to form a rectangle, sixteen a column and ten per row. What's that Michael? You don't know what's a rectangle? Billy? You're confused between the difference columns and rows. Yer Valars... (Barks a curt command to a group of uruks chatting around the water dispenser, taps foot impatiently) Now that is what I want. Now do as the Uruks just did. No Paul, you don't need to go growling and beating your chest, just go line up! Ok! You are now in a rectangle. No Jason! You don't go around giving hi-fives and handshakes, we're not over yet! Now I want the first four rows to point the sharpened ends of your big sticks forwards. What's that Billy? You still... Nevermind! The first four rows start with Andy and ends with Mac! You see that Billy? That's the first four rows! Now the rest of you tilt your sticks a little forward. Yes good. What's that Mac? You cannot point your stick forward because you'll impale the man before you and you don't want to impale him because you're a nice guy! Ok, just hold your stick over his shoulder. There! Now I want all of you to walk slowly towards that uruk over there. Nice and slow! Don't run Andy! WALK! Yes! Yes! Good... Now when you see those big bad strawheads and their horses, this is what you do. You pick up your big stick, form a rectangle and walk towards the strawheads together. Understand? Capisch? Good! Any questions? What's that Jason? Yes, you can go congratulate yourselves now!"