After exhausting all other alternatives, the Israel Defense Force (IDF) launched a military operation on December 27, 2008.
The Gaza Operation began with precision air strikes to minimize harm to civilians. But since Hamas refused to stop launching rockets against Israeli civilians, on January 3, 2009 the IDF commenced a ground action.
On January 17, 2009, in accordance with UN Security Council resolution 1860, the IDF withdrew all of its ground forces from the Gaza Strip.
Extended Answer