New Delhi, Aug. 3 -- TOKYO - For the first time in fifteen years, Washington and Tokyo agreed to move the yen together. Japan's Finance Minister Satsuki Katayama confirmed Monday that Thursday's intervention, which pushed the dollar-yen rate from the mid-160s to the lower 155 range in hours, was coordinated with the US Department of the Treasury. Japan did not act alone.

The scale of the action on Japan's side may have reached $44 billion, already the largest single-day currency market operation Japan had conducted in years. The coordination is what changes its meaning for markets.

Monday's announcement establishes Thursday as the first joint US-Japan currency market intervention since March 2011, when the G7 mobilized to cap a yen spik...