The South Korea-US alliance, formed 70 years ago in the wake of the Korean War, has evolved to be more than a military pact. It is a cornerstone for all aspects of the Seoul-Washington ties, encompassing the economy, culture and shared values.

The alliance’s beginning dates back to Oct. 1, 1953 when two sides signed the Korea-US Mutual Defense Treaty.

It was in the aftermath of the 1950-53 war on the Korean Peninsula, during which some 37,000 Americans died alongside South Koreans.

When the war broke out, with the invasion of North Korea on June 25 of 1950, the US was the first foreign country to enter the war to aid the South. It took just two days for the US to engage in the proxy conflict of the Cold War.

The post-war treaty forged between Seoul and Washington was a promise that they would provide mutual aid if either side is threatened by an external armed attack. It was also the basis of the US’ continued military presence on the Korean Peninsula until this day.

On top of military aid that would bolster South Korea’s defense against the North, the US would provide philanthropic support to help rebuild the war-torn country.

Richard Whitcomb, a late former US Army general, was at the forefront of these projects. Whitcomb devoted his life in helping establish hospitals and schools across country. He was awarded by the Mugunghwa Medal -- the highest Order of Civil Merit -- by the South Korean government last year.

The partnership with the US played a key role in South Korea’s economic development in the following decades.

The import of surplus agricultural products, mostly wheat, from the US in 1956 marked the reinstatement of international trade for the war-ravaged country.

Korea's industrial development was kick-started with financial aid from the US. During the Vietnam War from 1955-75, South Korea sent over 312,000 soldiers to fight alongside the US, which made it the largest dispatch of forces by a US ally. In return for their contribution, South Korea received multibillion-dollar investments from the US government. This aid provided the necessary capital for Park's ambitious economic development plan in the late 1960s and early 1970s, allowing South Korea to jump-start its economic growth.

The US also became South Korea’s main export destination from 1965 to 1969. It was the destination for some 50 percent of Korea’s outbound shipments of manufactured goods, such as wigs.

In terms of defense, the late '60s to early '80s was a time when the US was mulling the withdrawal of its troops from South Korea. It withdrew some of its troops from South Korea under the Nixon Doctrine implemented in 1969. Announced by former US President Richard Nixon, the doctrine aimed to shift the primary security burden to its Asian allies. The number of US military personnel in South Korea was reduced from 63,000 in 1969 to 43,000 in 1971 as a result.

President Jimmy Carter, who served in office from 1977 to 1981, also had a strong desire to pull US troops from South Korea.

However, on Nov. 7, 1978, the South Korea-US Combined Forces Command was launched to deter North Korean aggression and soothe South Korean fears of total withdrawal of US troops.

The alliance underwent another shift in the 1980s as the Cold War began to end and South Korea became a major player in the global economy. The changes ultimately led to Korea paying some of the costs of US deployments, such as local labor and military construction in the early 1990s.

Anti-American sentiment among the South Korean public reached its peak in the late 1990s and early 2000s. The sentiment was hit a nadir in 2002, when two 14-year-old girls named Shin Hyo-sun and Shim Mi-seon were killed in a traffic accident by a US military vehicle. The sentiment has largely died down since, with the 2019 Gallup Korea survey showing 77 percent of Koreans think favorably of the US.

Today, the alliance faces new challenges amid shifts in global geopolitics. South Korea has stronger ties with China, which is now its largest trading partner, but is engaged in a rivalry with the US. The geopolitics and the nuclear issues surrounding North Korea are now more volatile than ever.

Nodding toward this, President Yoon Suk Yeol said the alliance can “play a key role in overcoming crises that threaten world peace and prosperity," at a summit with US President Joe Biden in Washington on Wednesday.