Well like others sad - watch for those flanks.

And now something which the Phalangites can do better then thoose Legioneres - in thight street fighting they are almost as a wall of stone. Put them so that both flanks reach to the buildings on the side of the street so they can't be flanked and in Phalanx formation (with guard mod turned on! - they don't tire too quickly) you can hold back enemies several times of you number.

If you really want of a wall of doom you can put a second unit of Phalangites mixed "with another" just drag the cursor so the line of the second phalanx will be behind the second line of the first. - because since you have to "stretch" the unit so they reach the buildings on the end of the street one unit hardly makes two rowes of men but two phalanxes will make the min 5.

You should also try this when assaulting a city with wooden wall - just remember to send in a more mobile unit first to cover the Phalangites while they form up - otherwise they might be overrun