I have found a interesting site about dolphins and if they have a language, the website is http://www.thedolphinpod.com.
I have found this article in the web about if dolphins have really been trained by the US military:
Another trick some of the dolphins know is to stab enemy divers with a harpoon mounted on the animal's back, then drag the diver to the surface impaled upon the point. Another horror story, which appears to involve dolphins that were part of military experiments were the scores of dead dolphins that, washed up on French Mediterranean beaches. 'Earth Island Journal' (Summer 1998), reported that John Henley, a reporter for the London 'Observer' told of seeing most with "an identical, and mysterious wound, a neat, fist sized hole, on the underside of their necks."
Leo Sheridan, an accident investigator, is quoted as saying he is "convinced that these were dolphins that were trained by the US Navy, and something went badly wrong." Sheridan went on, saying "they were disposed of to conceal the existence of the American's military dolphin program." Apparently in 1989 the US began tests using dolphins fitted with special harnesses that would push electrodes into their flesh. The dolphins would be "monitored and controlled via electric signals transmitted through the neck harness." Most disturbingly, Sheridan pointed out that sixteen of the dead dolphins had wounds indicative of the explosive charge inserted into the harness worn by the military test subjects, to keep those dolphins from falling into enemy hands. "It seems incredible, but these programs are well known in military circles."