Buster Call

Buster Call is an emergency order which calls 5 vice admirals and 10 battleships from the marine headquarters to one spot. When you get targeted by a power of national war class, there'll be nothing left. Originally, it can only be used by the marine's three admirals and the Gensui (chief admiral)

CP9 was granted one opportunity to use Buster Call against the Straw Hats, under the name of admiral Ao Kiji.

Buster call is first mentioned in chapter 359, as Nico Robin explains why she left the Straw Hats.

Ohara
The Buster Call was seen in action 20 years ago in 1502 guided by Vice-Admiral Kuzan(Now Aokiji), and Sakazuki(Now Akainu). Other 2 Vice-Admirals are unknown but it's not known if Kizaru was one of these five Vice-Admirals presanted. Saul D. Jagaur was orginally going to be one of them but he desarted the Marines due to his oppostion on Absolute Justice

They manage to burn the whole island with an huge simple cannon, Saul manage to destory 5 Buster Call ships and the 6th ship was a exculative ship destoryed by Akainu.

After this, the World Government set blame on Robin for destroying these ship mainly to have the whole world go after her for reading Phonegyph.

Enies Lobby
20 years later, the Buster Call was summoned due to an clumsly mistake started by Spandam. As he dragged Robin while running he was angery that Luffy manage to catch up but blocked by Lucchi. He tried to call the rest of the CP9 to find out what is going on and why Luffy manage to make all the way but he accidently pressed the Golden Den Den Mushi.

Scared, Robin tries to warn the whole island of Marines and World Government Agents to flee, Spandam who believed that people should die in the name of Justice strucked Robin.

This Buster Call was runned by 5 unamed Vice-Admirals, it took them 30 minutes to arrive at Enies Lobby.