the deployment of Russian helicopters. Apart from the logistical challenges, the mission also faced problems of its impartiality and distinction from other troops and staff on the ground, especially in Chad. There was a concern about sufficiently differentiating the regular French soldiers who serve in Chad under the bilateral defence agreement between the two countries, the MINURCAT personnel and the EUFOR troops (the majority of whom were also French). Also, explaining the different roles of those forces to the local population and briefing of the troops on the complexities of the region was a major task. Rebel groups even threatened to attack any foreign force which they do not see as neutral, a threat clearly directed against France's dual role in Chad. This reiterated fears that the mission might be seen as a protection of the N'djamena regime. But the president of Chad, Idriss Déby, also accused EUFOR of collaboration with the rebels after the brief outbreak of violence around Goz Beida in June 2008. The accusation arose mostly from the narrowness of the mandate – criticised by both humanitarian workers and the Chadian government – which was not designed to interfere in the internal affairs of Chad (or to significantly improve security and development in the area). Paradoxically, Déby's critique after the June incidents strengthened the perceived neutrality of the mission. Sudan incident On 4 March 2008, two French soldiers in a soft-skinned Land Rover-type vehicle strayed 3 km into Sudan from Chad, and were fired upon by Sudanese forces. One of the soldiers was killed and reported missing while the other was wounded. Twelve French soldiers then entered Sudan to search for the missing soldier. They then came under fire, and fired back, killing one Sudanese soldier. The missing soldier's body was found by the Sudanese Army on 5 March, and was taken to Khartoum to be turned over to the French. However, one of the soldiers' grenades detonated as his body was being carried away, killing four Sudanese workers. Costs The operation came slightly under budget at €119.6 million (comparing to the planned €120 million, but originally envisioned at €99.2 million). This, however, was only for the common costs of the operation (mostly construction and operation of the camps), financed through the EU mechanism for financing military operations (Athena). The real costs are estimated to be between €400 and €500 million. In addition to these common costs