AFAIK that rotation trick was a difficult one to pull off, and required the somewhat demanding combination of comparatively loose order and well-trained troops. The Roman infantry did it, and it gave them a major edge against the disorderly barbarian hordes who crowded thick against the Roman line and the individual warriors couldn't retreat out of the way no matter how wounded or tired they became. That sort of thing is prime breeding ground for anxiety and eventually panic, with well-known results.

Phalanxes were probably way too dense to allow for that sort of rotation, but then again I've read a phalangite's most important traits were considered to be stamina and discipline, so the formation kept together and steadily and (fairly) tirelessly mowed down anything before it.

But then, the historical Ancient phalanxes tended to be huge affairs of thousands of men in a single rectamgular block hundreds of meter wide and up to sixteen ranks deep. The ones in Rome don't exactly compare...

As a side note the fairly small six-man deep pikeman rectangles the Swedish introduced into the Thirty Years' war seemed to hold their ground quite well against the huge, deep tercios most others initially used. Even if you factor in the considerable organic fire support they had, it makes you wonder if formation depth really is all that important in the "push of pikes".

...anyone feel like testing how well a long, thin line of phalangites does against a deeper, narrower phalanx in a head-on clash...?