The AHC, determined to prevent Resolution 181 from coming into effect, began to attack and besiege the Jews. The British sided with the Arabs in an attempt to prevent the Yishuv from arming themselves. Jerusalem was held under a siege with no access to weapons, food or water. The Provisional Government seemed helpless until it received a large shipment of arms from Czechoslovakia. The Haganah started fighting offensively from April through May. The Haganah mounted a full-scale military plan, Operation Nachson. After much fighting and the crucial construction of a new road from Tel Aviv to Jerusalem, the siege of Jerusalem was broken, allowing supplies to be brought into the city.