Parts of the army joined the rebels and weapon depots were plundered by protesters.[17] After initial advances by the rebels, the Libyan Army began a counteroffensive and started pushing back the rebel fighters.[18][19] On 17 March 2011, the United Nations Security Council passed United Nations Security Council Resolution 1973, authorizing the use of "all necessary means" to protect civilians in Libya, "excluding a foreign occupation force".[20] On Saturday, 19 March 2011, France began enforcement of the resolution by deploying French fighter aircraft over Libyan airspace.[21]