Operation Popeye first came to public light in March 1971, when reporter Jack Anderson published a story based on a secret 1967 memo from the Joint Chiefs of Staff to President Johnson. The memo read:  “Laos operations – Continue as at present plus Pop Eye to reduce the trafficability [sic] along infiltration routes & Authorization requested to implement operational phase of weather modification process previously successful tested and evaluated in some area“. (US Senate, Subcommittee on Oceans and International Environment; 26 July 1972; p. 5).

Members of Congress pressed the Pentagon to unveil details of the weather modification program. Senator Claiborne Pell, chairman of the Senate Subcommittee on Oceans and International Environment, and later chairman of the Foreign Relations Committee, was the engine behind that effort, although there were others, both in the Senate and the House, who devoted energy to it.

Rainmaking operations were a source of concern not only because the impact of the operations themselves, but because they were seen as opening the door to a new and dangerous type of warfare. Severe rains and typhoons in North Vietnam in 1971 added to concern, a link to the U.S. cloud seeding operations was suspected.   According to Pell:

Rainmaking as a weapon of war can only lead to the development of vastly more dangerous environmental techniques whose consequences may be unknown and may cause irreparable damage to our global environment. This is why the United States must move quickly to ban all environmental or geophysical modification techniques from the arsenals of war 

(US Senate, Subcommittee on Oceans and International Environment; July 26, 1972; p. 4)  

Read full report at:  http://www.sunshine-project.org/enmod/US_Congr.html