Battle Tactic: Stairway to Hell
Place four legion squares in echelon, with each just to the the left rear of the one in front. The northeast corner of each, touches the southwest corner of the square to it's front and right. Place your javelins in front of the whole array.
As the enemy moves toward you, withdraw the firing javelins out of harms way, by zig zagging them back and forth across the echeloned array of Legion squares. As the enemy pursues your javelin troops to prevent their firing, they will be lured into a succession of legions squares through which the javelin troops withdraw.
The echelon deployment has the advantage of forcing the enemy to stretch his front very thin in order to engage or envelope the lengthy oblique line of squares. His stretched and scattered force is easier to defeat. Also, any enemy force attacking one square, will find another engaging his flank. If the enemy tries to engage each square one at a time, with his whole force, to beat them in detail, than javelin troops protected by the other following squares not yet engaged will continue to fire on him without hindrance. Moreover, the unengaged squares can be brought forward against the flank of the enemy units besieging the first square.
The enemy can't outflank this stairwell formation, since it has too much surface area.
The javelins can zig zag from one side to the other seeking the protection of the squares and they retreat back and forth across them. Although the javelins are shown in horizontal rows, feel free to shift them into vertical columns, as they zig zag through the squares. The proximity of the enemy, the best targeting angle etc. will determine whether the vertical column of horizontal row is best, at any given moment.