Hoplites fighting in Phalanx formation

[Tarbicus]

One side broke and its soldiers (surprisingly) fled. Often only part of the battle line fled, while the rest was still fighting and sometimes they won in spite of the flight of their fellow soldiers....How is this possible that they always fled? Moreover if all the Greeks were so painstakingly trying to support their comrades and not to look cowardly in the eyes of their fellow citizens, why was it important to have the special, brave rear rankers to prevent the escape of the (say) less brave men?

Not quite. They also surrendered. The Macedonian phalanx, at least, had a surrender signal which was to raise all of their pikes.