 Complete the following phrase:  Phalanxes facing the legion were vulnerable to the more flexible Roman checkerboard deployment, which provided each fighting man a good chunk of personal space to engage in close order fighting. The manipular system also allowed entire Roman sub-units to manoeuvre more widely, freed from the need to always remain tightly packed in rigid formation. The deep three-line deployment of the Romans allowed combat pressure to be steadily applied forward. Most phalanxes favoured one huge line several ranks deep. This might do well in the initial stages, but as the battle entangled more and more men, the stacked Roman formation allowed fresh pressure to be imposed over a more extended time. As combat lengthened and the battlefield compressed, the phalanx might thus become exhausted or rendered immobile, while the Romans still had enough left to not only manoeuvre but to make the final surges forward. Hannibals deployment at 