A new milestone was reached last week in the growing U.S.-India partnership when nearly 2,000 troops from the two countries completed a military exercise in the Bay of Bengal

About 500 Marines and sailors aboard the dock landing ship Germantown joined roughly 1,200 Indian troops for Exercise Tiger Triumph. It was the first time all of India's military services, including the army, navy and air force, participated in a training exercise with U.S. troops.

The nine-day exercise ended on Nov. 21.

The U.S. and India signed a defence agreement last year. Then-Defence Secretary Jim Mattis said at the time the two countries would "work together for a free and prosperous Indo-Pacific."

Military leaders and defence experts have stressed the importance of a strong partnership between the U.S. and India as China's influence in the Asia-Pacific region expands. A January Pentagon news release calls the U.S.-India defence relationship "indispensable in promoting peace, prosperity and stability in the Asia Pacific and Indian Ocean region."

The U.S. declared India a major defence partner in 2016.

During Tiger Triumph, U.S. troops sailed aboard Indian ships and Indian troops on the Georgetown to "[gain] exposure to their partners' naval capabilities," according to a Marine Corps video on the exercise. The ships sailed from Visakhapatnam along India's east coast about 100 miles south to Kakinada.

An Indian UH-3H Sea King helicopter landed aboard the USS Germantown during the exercise, and there was live-fire training on the ship. The troops also practised moving ashore to respond to a humanitarian crisis.

President Donald Trump spoke about the exercise during a September rally in Houston where he appeared alongside India's Prime Minister Narendra Modi. The event was billed as "Howdy, Modi: Shared Dreams, Bright Futures."

"In November, the United States and India will demonstrate a dramatic progress of our defence relationship, holding the first-ever tri-service military exercise between our nations," Trump said. "It's called 'Tiger Triumph.' Good name. ... We honour all of the brave American and Indian military service members who work together to safeguard our freedom."

While many see a U.S.-India partnership as a vital step in countering China, the relationship has been complicated when the country decided to move forward with a decision to purchase S-400 Triumf anti-air missiles, which Moscow bills as "F-35 killers."

But last year, Adm. Phil Davidson, head of U.S. Indo-Pacific Command, warned Congress against the U.S. sanctioning India over the move, saying the partnership between the two countries to counter China should take precedence.

"If the United States decides to sanction these partner nations for their purchases of Russian equipment, this decision may hinder the growth of each developing partnership and increase each partner's dependence on Russia," Davidson told lawmakers.

Last year, Mattis announced that U.S. Pacific Command was being renamed INDO-PACOM "in recognition of the increasing connectivity between the Indian and Pacific oceans." As Reuters noted at the time, the move was seen as a symbolic nod to India and its growing importance to the Pentagon.