The Late Heavy Bombardment (LHB) is a cataclysmic period of intense asteroid and comet impacts on the Moon and other inner planets, occurring about 700 million years after the formation of the terrestrial planets. This event is not naturally explained by current planetary formation theories. A new model proposes that the LHB was triggered by the rapid migration of the giant planets, which occurred after a long quiescent period. During this migration, the planetesimal disk outside the orbits of the planets was destabilized, causing a sudden massive delivery of planetesimals to the inner Solar System. The asteroid belt was also strongly perturbed, with these objects supplying a significant fraction of the LHB impactors. The model not only explains the LHB but also reproduces the observational constraints of the outer Solar System. The model suggests that the LHB was caused by the giant planets crossing the 1:2 mean motion resonance (MMR) roughly 700 million years after they formed. This crossing led to a temporary destabilization of the giant planets, resulting in close encounters among Saturn, Uranus, and Neptune. These encounters, along with interactions with the disk, caused Uranus and Neptune to reach their current heliocentric distances and Jupiter and Saturn to evolve to their current orbital eccentricities. The model also shows that the LHB was caused by a mixture of comets and asteroids. The asteroid belt was depleted by a factor of about 10 during the LHB, which is consistent with collisional evolution models. The LHB lasted between 10 and 150 million years, with a sharp increase in impact rate at the beginning of the LHB. The model predicts that the LHB impactors were a mixture of comets and asteroids, with comets dominating in the first 30 million years and asteroids in the later stages. The model also supports the current observed planetary orbits and the origin of Jupiter's Trojans.The Late Heavy Bombardment (LHB) is a cataclysmic period of intense asteroid and comet impacts on the Moon and other inner planets, occurring about 700 million years after the formation of the terrestrial planets. This event is not naturally explained by current planetary formation theories. A new model proposes that the LHB was triggered by the rapid migration of the giant planets, which occurred after a long quiescent period. During this migration, the planetesimal disk outside the orbits of the planets was destabilized, causing a sudden massive delivery of planetesimals to the inner Solar System. The asteroid belt was also strongly perturbed, with these objects supplying a significant fraction of the LHB impactors. The model not only explains the LHB but also reproduces the observational constraints of the outer Solar System. The model suggests that the LHB was caused by the giant planets crossing the 1:2 mean motion resonance (MMR) roughly 700 million years after they formed. This crossing led to a temporary destabilization of the giant planets, resulting in close encounters among Saturn, Uranus, and Neptune. These encounters, along with interactions with the disk, caused Uranus and Neptune to reach their current heliocentric distances and Jupiter and Saturn to evolve to their current orbital eccentricities. The model also shows that the LHB was caused by a mixture of comets and asteroids. The asteroid belt was depleted by a factor of about 10 during the LHB, which is consistent with collisional evolution models. The LHB lasted between 10 and 150 million years, with a sharp increase in impact rate at the beginning of the LHB. The model predicts that the LHB impactors were a mixture of comets and asteroids, with comets dominating in the first 30 million years and asteroids in the later stages. The model also supports the current observed planetary orbits and the origin of Jupiter's Trojans.