Juan Cole criticizes partitioning as a way of dealing with Iraq's problems

And other conflicts, too:

But partitions are rare in in the post-war era. And the few that have occurred don’t offer encouraging examples. The United States was all enthusiastic to break South Sudan off from Sudan proper, in order to weaken one of Africa’s larger states and given that the Christian and animist population there had long chafed under northern Muslim Arabophone rule.

But no sooner was South Sudan independent than it was largely abandoned by the US and it fell into a vicious and brutal civil war between the Dinka and Nuer ethnic groups. Moreover, its post-independence dispute with Khartoum led the latter to block its oil exports.

So the takeaway is that a partition can often actually lead to more conflict.