We present a global description of the dynamics of the Trojans in tadpole orbits. Beside the s6 secular resonance, known for more than twenty years, we show that three different families of resonances structure the Trojan's space phase. The connection and the overlapping of certain of these resonances generate long time diffusion, which would drive certain Trojans from the inner part of the libration region to the horseshoe region. As the location of the resonances changes under a modification of the basic frequencies of the planets, we show how the resonant structure would evolve during a migration of Jupiter and Saturn.