As an example you can look what happened to XP territories during last TW - 4 factions attacked them but they focused only on one (HO) so other 3 (Girls, Voodoo, ThaClick) could attack them and gather some lands.
Same can be done with other territories, against other factions like Worms/HO - if few factions gonna attack them they wont be able to defend all of those. Or u can bid on smaller factions which are on TW map atm.