CAUSES OF CONFLICT:

There are three basic causes to the Iraqi invasion of Kuwait in 1990. First, Iraq had long considered Kuwait to be a part of Iraq. This claim led to several confrontations over the years (see below), and continued hostility. Also, it can be argued that with Saddam Hussein’s attempted invasion of Iran defeated, he sought easier conquests against his weak southern neighbors.

Second, rich deposits of oil straddled the ill-defined border and Iraq constantly claimed that Kuwaiti oil rigs were illegally tapping into Iraqi oil fields. Middle Eastern deserts make border delineation difficult and this has caused many conflicts in the region.

Finally, the fallout from the First Persian Gulf War between Iraq and Iran strained relations between Baghdad and Kuwait. This war began with an Iraqi invasion of Iran and degenerated into a bloody form of trench warfare as the Iranians slowly drove Saddam Hussein’s armies back into Iraq. Kuwait and many other Arab nations supported Iraq against the Islamic Revolutionary government of Iran, fearful that Saddam’s defeat could herald a wave of Iranian-inspired revolution throughout the Arab world. Following the end of the war, relations between Iraq and Kuwait deteriorated; with a lack of gratitude from the Baghdad government for help in the war and the reawakening of old issues regarding the border and Kuwaiti sovereignty.

http://www.historyguy.com/GulfWar.html