 The rockets were also used several times (over a thousand stockpiled) by Polish freedom fighters during the final Battle of Warsaw (September 1831) in defense of the city.Congreve rockets were used from the bombardment of the Canton ports, by Nemesis (1839) in January 1841, to their use at the Battle of Palikao, in September 1860.During the period of the New Zealand Wars, the British Army used Congreve rockets to attack Māori fortifications—along with cannon fire—but found that simple trench-warfare practices were sufficient to blunt their effectiveness so much that, like cannon, they were virtually useless.