I think I got it from the Romans in Asterixdictionary.com says
A body of heavy-armed infantry formed in ranks and files close and deep. There were several different arrangements, the phalanx varying in depth from four to twenty-five or more ranks of men.
(A body of heavy-armed infantry formed in ranks and files close and deep. There were several different arrangements, the phalanx varying in depth from four to twenty-five or more ranks of men.
littlebean,
Tue 8 Oct 2002, 10:27,
archived)