Some states, like Israel and USA, has carried out preventive attacks on other states’ nuclear programs. The attacked stated have been autocracies rising in power with a violent history and with a different political orientation than those attacking. However, there are states that have fulfilled the same criteria, but that has not been attacked. What motivates a state, due to relative power, to attack another states’ nuclear program? Israel has attacked nuclear plants both in Iraq and Syria, two autocratic states that has been aggressive towards Israel. Iran, which is another state that is acting aggressive towards Israel and has a developing nuclear program, has not been preventively attacked. The purpose of this study is to find out what generally motivates states to attack nuclear programs, and particularly why Israel in particular has not bombed Iran’s nuclear program. A comparative case study with text and data analysis has been used. The comparison is between Iraq in 1981 and Iran 2009-2013 and the analysis consists of questions about Iraq and Iran in relation to Israel about regime type, military capacity, threats and violent conflicts. The result of the analysis shows that Israel has not attacked Iran because there is no history of violent conflicts between the two countries. Israel, on the other hand, has been at war with Iraq several times. Increasing power in a state that possesses nuclear weapons appears more threatening if there is a history of violent conflicts. This is probably the case with Israel and Iran since the definition of power in this study handles only military capability. More investigation on the subject is needed due to this narrow definition of power.