Relations between countries are not set in stone.
Old friends can become bitter rivals and former enemies can become close allies.
And as these relationships change, so too do the foreign policy tools
the countries use to interact with and influence each other.
Just take a look at how U.S.
foreign policy toward Japan has dramatically shifted
over the past century.
In the early 1900s, Japan and the United States were increasingly becoming rivals.
The two rising powers were expanding the areas they controlled, with the U.S.
reaching westward
across the Pacific and Japan taking over large parts of East Asia.
Over time, U.S.
leaders became concerned that continued Japanese expansion would threaten U.S.
interests in the region.
So the U.S.
used its foreign policy tools to push back against Japan.
This included the United States push for arms control in the early 1920s.
U.S. leaders, along with the European powers, convinced Japan
to sign a multilateral agreement limiting the size of their navies
and banning the construction of any new naval bases in the Pacific.
In the early 1930s, though, U.S.
leaders remained concerned and relied on diplomacy
to try to discourage Japan from conquering certain parts of China,
criticizing Japanese aggression and announcing that the U.S.
would not recognize any position Japan gained through force.
This was
echoed by the British and other Europeans.
Nevertheless, Japan continued its aggression and the U.S.
placed military and economic sanctions on the country,
cutting off access to the Dutch East Indies, a lifeline for the Japanese,
and banning the export of American oil to Japan
, which was critical for the Japanese military and economy.
While diplomats from both countries tried to negotiate
an end to the dispute, Japanese leaders came to believe war with the U.S.
was their best option.
So they decided to strike first in December 1941
with a surprise attack on Pearl Harbor and other U.S.
territories in the Pacific.
The U.S.
responded by declaring war and began using armed force
against Japan officially entering World War Two.
While Japan quickly
conquered much of the Western Pacific and Southeast Asia, the U.S.
was ultimately able to roll back the Japanese advance.
Still, the U.S.
and its allies demanded Japan's unconditional surrender
in order to ensure that it wouldn't threaten the region again.
At first, Japanese leaders refused.
But in 1945, after the U.S.
dropped two atomic bombs on the cities of Hiroshima and Nagasaki,
and after the Soviet Union also declared war
on the country, Japan's leaders surrendered.
The U.S.
military occupied Japan and the United States engaged in nation building.
Drafting a new constitution for Japan that built the foundation
for its current democracy and limited what it could do to rebuild its military.
After the war, though, U.S.
foreign policy changed dramatically and the once bitter enemies
became close allies.
After World War Two, the United States found itself in its Cold War competition
with the Communist Soviet Union and the new communist regime in China.
And U.S.
leaders sought to prevent communist expansion around the world.
Within a few years, U.S.
leaders realized
that Japan could be strategically useful in checking that expansion in East Asia.
And they used foreign policy tools with the goal of building up
Japan as a strong partner against the communist countries.
Japan's military had been dismantled after the war,
and the country's new constitution restricted how
it could rebuild its military, leaving it relatively weak.
But U.S.
leaders practiced deterrence by offering Japan a security treaty where the U.S.
agreed to defend Japan from any attack, thus discouraging any
country from attacking Japan.
The U.S.
also supported Japan as it developed its military capabilities
under the rubric of self-defense forces bolstering that deterrence.
Meanwhile, U.S.
leaders used foreign aid, providing hundreds of millions of dollars
worth of assistance to help Japan rebuild its economy
even after the occupation ended in 1952.
U.S. officials continued
to support the country through trade policy, encouraging foreign investment
into Japan and giving Japanese exporters access to U.S.
and European markets.
The U.S.
had more than achieved
its foreign policy goal of making Japan into a strong partner.
In fact, by the 1980s, the Japanese had built the world's second largest economy,
and by the end of the Cold War, Japan was cooperating with the U.S.
and its allies in their competition with the Soviet Union.
But with the Cold War over by 1991 and the Soviet threat gone, U.S.
foreign policy priorities shifted once again,
and some cracks in the US-Japan relationship deepened.
Japan's economic growth was so strong
that the United States increasingly saw it as a major economic competitor.
And U.S.
policymakers used their foreign policy
tools accordingly, negotiating new trade agreements with Japan
to allow American companies greater access to Japanese markets.
And the U.S.
even threatened to use economic sanctions against Japan
to settle some trade disputes.
Nevertheless, the U.S.
and Japan remained close partners on many international issues.
Both countries worked together on arms control efforts,
negotiating unsuccessfully with North Korea
to try to stop it from building nuclear weapons.
Japan increasingly relaxed its restrictions on its military,
which is now one of the most capable in the world, and worked closely
with the United States and other allies in their fight against terrorism.
After 911.
Japan also contributes forces to U.N.
peacekeeping operations around the globe.
And both Japan and the U.S.
regularly conduct joint military exercises showing off their partnership
and strength as a way to deter Chinese aggression in the region.
Recent U.S.
presidents have emphasized the importance of the U.S.
Japan alliance, calling it a cornerstone of peace and security in the region.
In a matter of decades, the United States and Japan went from dropping bombs
on each other to forging remarkably close political, economic and military ties.
This goes to show that relations between countries
evolve and his foreign policy goals change.
So too do the tools the countries use to achieve their aims.