Cadan first saw field combat against the Guyver some time after the D-59 Incident, but barely got the chance to fight as the Zoanoid platoon was quickly vaporised by the Guyver's Mega-Smasher. Other Cadan units would appear during the Takeshiro Incident, but again were swiftly eliminated by Guyver-III. Success against the Guyvers wasn't expected by then since production class Zoanoids had repeatedly failed many times before then.
Against human opponents, however, Cadan proved to be most effective. During X-Day, Cadan units were deployed against the US Navy to great effect.