By Gideon Rachman
The assault on the Iraqi city of Mosul that began this week underlines the fact that the next three months will be a perilous period in international politics. Fighting is intensifying in the Middle East. Tensions are rising between Russia and the west. And relations between China and its Asian neighbours are getting edgier. All this is happening while the US is diverted by the Trump-Clinton melodrama and the transition to a new president.