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Protesters gather in kayaks outside Pentagon
The Backbone Campaign, along with the World Beyond War, organized the event, which featured protesters in kayaks gathered at the Pentagon Lagoon holding signs that read "No oils for wars! No wars for oil!"
The protest comes ahead of the movement's conference "No War 2017: War and the Environment," on Sept. 22-24 in Washington, D.C.
Manning, who in 2013 was convicted of leaking hundreds of thousands of classified documents, is listed as the special guest, while Snowden is listed as a speaker by video.
Other speakers included former Green Party presidential nominee Jill Stein, Code Pink co-founder Medea Benjamin, and Daniel Ellsberg, who is known for releasing the Pentagon Papers.