Subrahmanyam Jaishankar on Sunday ended his three-year tenure as Foreign Secretary, with the Assomption Island treaty with Seychelles as his last assignment. Appointed to the post in 2015, Jaishankar is reportedly the longest-serving foreign secretary since 1976. During his foreign service, he played a key role in the US-India nuclear deal and also negotiated the Doklam standoff with China.