Throughout his career, Gromyko explicitly promoted the idea that no important international agreement could be reached without the Soviet Union's involvement. Towards this end, one accomplishment he took particular pride in was the signing of the 1963 Partial Test Ban Treaty whose negotiation could be traced back to 1958. Additionally, in 1966, Gromyko and Alexei Kosygin persuaded both Pakistan and India to sign the Tashkent Declaration, a peace treaty in the aftermath of the Indo-Pakistan war of 1965. Later in the same year, he engaged in a dialogue with Pope Paul VI, as part of the pontiff's ostpolitik that resulted in greater openness for the Roman Catholic Church in Eastern Europe despite heavy persecution of Christians in the Soviet Union itself.