Who violated the ceasefire?

"Sources in the defense establishment said Defense Minister Ehud Barak instructed the Israel Defense Forces to prepare for the operation over six months ago, even as Israel was beginning to negotiate a ceasefire agreement with Hamas. According to the sources, Barak maintained that although the lull would allow Hamas to prepare for a showdown with Israel, the Israeli army needed time to prepare, as well. Barak gave orders to carry out a comprehensive intelligence-gathering drive which sought to map out Hamas' security infrastructure, along with that of other militant organizations operating in the Strip."