You can 'liaise with' people and you can 'liaise between' them. No-one ever liaised against anybody, which makes it an ideal verb for the haven of peace and tranquility that is modern business. Despite these pacifist tendencies, however, 'liaise' is a military word. In World War I, French liaison officers formed links between the allied forces, using the Gallic term for relationships of all kinds. British ingenuity turned that into the verb 'to liaise', first recorded in 1916 in a letter from Lord Fisher, First Sea Lord. It was demobbed only after World War II. Interestingly, 'liaison' retains its Continental, raffish air, while 'to liaise' is pure in thought, word and deed. 'I'll liaise with you later, Susie', you say, and no-one turns a hair. Suggest a liaison, however, and Susie will be consulting her pamphlet on sexual harassment quicker than you can say 'inappropriate behaviour'.