From what I understand, the Gracchi argued that successful Roman military conquest had resulted in an influx of slave labor, which in turn allowed the patricians to consolidate and expand their land holdings in Italy, driving the peasantry into the cities and swelling population of urban poor. Land redistribution and the introduction of the grain dole were meant to alleviate this. Do modern historians agree with this explanation? Or do they see other causes as being the primary drivers of urbanization?