This paper analyzed how Japan and South Korea consider the U.S. as their ally
by using the SIE and threat effects. South Korea considers the United States as an
important ally during all periods, but Japan began to form a close relationship with the
United States only recently. South Korea is found to be a less important ally to the U.S.
than Japan according to SIE estimates.
In response to threats from the China-North Korea alliance. South Korea did not
increase military expenditures, whereas Japan and the United States showed positive
responses to recent increases in the threat posed by this alliance. The recent Japanese
reactions to threats from the China-North Korea alliance have been particularly
sensitive, as compared with those during the earlier sample periods. This implies that
Japan and the United States have begun to respond more actively to the recent increase
in military expenditures spent by the China-North Korea alliance.
This paper suggests that the three countries hold different views of the threat from
the China-North Korea alliance