Hamas is a Palestinian state-sponsored terrorist organization whose stated purpose is to destroy the state of Israel. They have recently broadened this to also killing Jews and Americans wherever they are, as well as anyone who doesn't support them.
Their goal is not to negotiate a Palestinian state next to Israel - it is to destroy Israel. They have stated this clearly and repeatedly.
Their strategy is to kill as many Israelis as possible. Since civilians are usually easier targets than soldiers, they mostly kill civilians. Since public places are usually easier to target than military locations, they target public places. Since they have no respect for any life, their own or anyone else's, they send suicide bombers to public areas and shoot rockets at schools and hospitals (and from them as well).
They have gained control of Gaza, but spend their time, effort and money acquiring and shooting weapons at Israel rather than improving the lives of their people - they claim to have no food, yet they have plenty of weaponry.
Israel, on the other hand, has frequently been publicly denounced of killing innocent civilians, though the fact of the matter is that they have been attacking terrorist leaders who have been hiding in civilian buildings. It is also true that Israel has been destroying civilian infrastructure. This was done because members of the terrorist organizations have been using this infrastructure to support their attacks on Israel.
Clearly, the terrorists (including Hamas), are the attackers. Israelis are defending themselves from men devoted to destroying their homes.
Israel is innocent. Hamas is not.
Hamas has declared an unceasing war against the Jewish people, but has only attacked them in Israel.
Israel.
Hamas refuses to recognize Israel whereas the previous Palestinian party in power, Fatah, is willing to recognize Israel and negotiate with them to degree. Therefore, when Hamas replaced Fatah as the legitimate government of the Palestinians by elections in 2006, Israeli relations with the Palestinian Authority soured in anticipation of the more doggedly Anti-Israel stance of Hamas.
ISRAEL
Mainly Hamas, Hizbollah, Syria and Iran.
Hamas dictatorship which was created by the nation of Israel.
Israel was right because Hamas was constantly attacking them. Note: The above answer is referring to the confrontation between Israel and Hamas called Operation Cast Lead which occurred in December of 2008 and January of 2009. In 1914, there was no such political organization as Hamas and there was no government called Israel. Therefore, the question as actually posed is meaningless. There were Jewish and Palestinian Militias operating in Ottoman Palestine at the time, but they were in their infancy and more directed against the Ottomans than against each other.
Gaza is in the control of Hamas (a Palestinian group), West Bank is still in the hands of Fatah (another Palestinian group) but Israel is the occupying force in the vast majority of the West Bank.
Israel invaded the Hamas-controlled Gaza Strip from December 2008 to January 2009.
the hamas is using them as human shields to fire rockets at israeli cities
Floor Janssen has written: 'Hamas and its positions towards Israel'
The conflict between Israel and Gaza was caused due to Hamas being elected into power in Gaza in 2005. In Hamas' charter, it calls for the destruction of the Jewish state (Israel). Israel and America, in trying to get the Palestinians to the negotiating table, mistakenly withdrew from Gaza as a goodwill gesture, but didn't expect Hamas to get elected. Hamas is the Palestinian branch of the Muslim Brotherhood, and as such vehemently opposed to any nation, anywhere in the world, which has any kind of rule other than Shari'ah (Islamic law). The conflict between Israel and Gaza is no different to the conflict and violence caused by Muslims in India, Nigeria, Kenya, Somalia, Thailand, the Philippines etc.