Complex sentence: Britain's intelligence agency Government Communications Headquarters (GCHQ) took part in the program, targeting several anti-Vietnam War dissidents such as Tom Hayden and Jane Fonda, and handing over intercepted data of Americans to the U.S. government.
Split into simpler sentences: Britain's intelligence agency Government Communications Headquarters (GCHQ) took part in the program, targeting several anti-Vietnam War dissidents such as Tom Hayden and Jane Fonda. The GCHQ handed over intercepted data of Americans to the U.S. government.