It's not easy to annex a land . A war is not cheap but extremely expensive , and also its not video game or movie dear brother.
In this modern world no body can totally win a war , or if it wins , the win comes at the expense of huge bloodshed , and also economy is under heavy threat . look at USA . It is not attacking Iran , because Iran is not the iraq of saddam Hussein ( both time ) , but Iran is completely different thing .
USA can defeat Iran , but will be a huge burden on USA that they can hardly bear .
Although Trump behave like a mental patient , but he is actually very cunning and he knows the consequence of war , that's why he is not attacking Iran . So war should be the last resort .I hope you understand that . Thanks and peace.
@CHACHA"G"