What was President George H.W. Bush's most important foreign policy?
Since your other questions were about the 1990s, I am assuming you are asking about President George H. W. Bush. I have changed your question accordingly.
The most important foreign policy of the first President Bush was his policy regarding the Iraqi invasion of Kuwait. Bush’s policy in regard to this event had three aspects that were very important. First, Bush was able to put together a large coalition to oppose Iraq. Very importantly, this coalition included Arab countries, thus preventing a situation in which the war would be seen as an act of Western aggression against a Muslim country. Second, during the war, Bush was able to persuade Israel to refrain from getting involved. This was true even when Israel was attacked by missiles from Iraq. By keeping Israel on the sidelines, Bush managed to keep Arab consent to the war. Finally, Bush decided not to expand the war after Iraq had been expelled from Kuwait. Bush chose not to invade Iraq and topple Saddam Hussein.
These policies were, for better or for worse, the most important of President Bush’s term in office. There were other foreign issues that arose, such as the dispute that led to the invasion of Panama, but the reaction to Iraq’s invasion of Kuwait was by far the most important.