SEOUL — America and its South Korean ally have joined forces in a military exercise here without firing a shot, searching computers, or barking orders in make-believe battles. They did, however, march together.

The occasion, which was witnessed by your intrepid correspondent, was a parade Tuesday through central Seoul. It marks the first time in the 70-year history of the Korean-American alliance that Americans have participated with Koreans in such an event. 

The Americans, including about 300 army soldiers, sailors, airmen and marines, formed tight formations behind the band of the 8th United States Army. That’s the top command that includes most of the 28,500 American troops in Korea other than those in the Air force and Navy.

The decision to include Americans in a military parade, the first here in a decade, symbolized the tightness of the bond that’s solidified between the Americans and South Koreans since the election of the conservative Yoon Suk-yeol as president by a slim margin in March of last year. 

To thousands of Koreans lining the parade route in pouring rain, and many more who avoided the weather by watching from high-rise office buildings, the parade dramatized the close cooperation that Americans and Koreans have displayed in recent joint military exercises.

Mr. Yoon has sanctioned the exercises after his liberal predecessor, Moon Jae-in, canceled them while searching for dialogue and reconciliation with the North Korean communist party boss, Kim Jong-un.

The crowd formed a sea of umbrellas as they pressed against barricades set up to clear the broad avenue leading from the city’s historic Namdaemun, or South Gate, toward the ancient Gyeongbok Palace, the heart of the dynasty that ruled Korea for more than 500 years until the onset of Japanese colonialism in 1905.

The parade was South Korea’s answer to North Korean parades featuring, recently, intercontinental ballistic missiles capable of hitting targets in North America.  The Americans, in combat fatigues, slogged along after Korean troops in the full-dress uniforms of all branches and special units. 

Cheers  burst out as the South Koreans showed off their latest military hardware.  In the forefront was a vanguard of heavy weaponry, including Hyunmoo mid-range missiles for hitting targets anywhere in North Korea and L-Sam missiles for shooting down North Korean missiles that Mr. Kim frequently threatens to rain on the South

South Korea’s heavy weaponry, as seen in the parade, also included 60-ton K-2 tanks modeled after America’s vaunted Abrams, drones  of varying shapes and sizes, at least one underwater ballistic missile, and rockets and artillery pieces designed and made in South Korea. 

The only disappointment was the weather forced cancellation of a display of derring-do by the Black Eagles flying T-50 fighter planes, made in Korea, performing figure eights and other maneuvers. Nor could Apache helicopters roar to their simulated targets — the best part of a great show that I witnessed Saturday at Seoul Air Base.

The crowds did get to see President Yoon at the parade, marching and waving beside his defense minister, Lee Jong-sup, in carefully scripted contrast to the North Korean leader, Kim Jong-un, who stays high above the crowd, surrounded by bemedaled generals and security guards.

Mr. Yoon, in his speech at Seoul Air Base, sounded off in rhetoric that came in response to Mr. Kim’s speeches in which he said he would destroy the South with nuclear warheads if American and South Korean forces attack the North.

South Korea’s Yonhap News quoted Mr. Yoon as warning, “the North Korean regime must clearly realize that nuclear weapons will never be able to guarantee its security.” If the North were to use its nukes, he said, “ its regime will be brought to an end by an overwhelming response from the South Korea-U.S. alliance.”