This entry, and its predecessor in Photius (sigma605 Theodoridis), are derived from the entry stratei/a in Timaeus' Platonic Lexicon (a fact which does not, however, guarantee that the ultimate origin of the entry is in Plato). On this basis, Theodoridis prints the headword in Photius as stratei/a, although it would be out of alphabetical order. (Both these lexica have entries for stratia/ with the gloss that appears in the Suda at the beginning of sigma 1175.)
*stratei/a, as the nomen actionis from the verb strateu/w (sigma 1164), usually means an expedition or military campaign. *stratia/ can bear this meaning, but primarily means an army. See LSJ s.v. stratei/a (end), and cf. sigma 1165, sigma 1166.