Israel at a relatively low price. In place of the IIA, the Vautour IIB was procured instead, which was suitable for performing level bombing runs across all altitudes, as well as the low altitude toss bombing attack profile. To address a deficiency of the Vautour that had been determined mid-service life, this being its limited range in comparison to contemporary strategic bombers, considerable emphasis was placed upon the introduction and perfection of aerial refueling techniques in the AdA. This led to the adoption of a 'buddy pack' to enable pairs of Vautours to refuel one another in mid-air, allowing for the range factor to be better addressed. A fleet of 40 AdA-operated Vautour IIBs constituted the original air-based component of the French force de frappe, the Commandement des Forces Aériennes Stratégiques (CFAS) of the French Air Force, which had been established during 1955. However, their use in the strategic bomber role was determined to be less than optimal; allegedly, the Vautour's performance was commonly considered to be marginal and suitable for use as a stop gap measure at best. The deficiencies of the type contributed to France issuing a more stringent requirement calling for a new high performance bomber aircraft to be developed to perform the strategic mission. While efforts were made by Sud Aviation to design improved variants of the Vautour to conform with the new demands, the AdA opted to pursue rival aircraft company Dassault Aviation's proposal, which eventually resulted in the deployment of the Mirage IV, which eventually succeeded the Vautour in the bombing role in French service. As early as 1955, preliminary agreements for Israel's procurement of the Vautour were being drawn up and advanced plans being laid for its deployment. During early 1957, the type was officially selected to replace the British-built de Havilland Mosquito then in service with the Israeli Air Force (IAF). On 1 August 1957, the first Vautour arrived in Israel, delivered secretly via French air bases in Tunisia and with AdA markings. The planes were delivered at a rate of 1 or 2 per month. Their entry into service had allegedly been delayed by several months due to political issues between Israel and France, which was resolved when permission to commence operations was granted by the latter. Deliveries of the type were completed in 1958. During August 1958, the existence of Israeli Vautours was publicly revealed in an air display. Crosbie