An understanding of past events can help us see what might happen in the future, if only because history reveals something of the timeless psychology of individuals, nations and governments.
When America's Vietnam campaign was becoming bogged down under the pressure of a geurilla army, US policy developed in two ways. First, the war was intensified inside Vietnam through a massive escalation of troops. Second, the war was widened geographically into Cambodia and Laos.
Both developments are currently taking place in America's middle east campaign. Driven by an ideological commitment to extend American political and economic influence in the region, the US military commitment is being extended numerically.
At the same time, the pretext for extending the war to Iran is being carefully and deliberately laid. The excuse will be alleged Iranian support for Shia militias. The driving force behind an attack, however, will actually be fear of Iranian nuclear ambitions.
An invasion of Iran is highly unlikely. Selected air strikes against nuclear facilities is almost a certainty.
Beyond that, keep an eye on Somalia. American forces have already been in action there in recent weeks. This is likely to recur if Islamist groups manage to grow in strength in that nation.
A comparison with Vietnam indicates one further possible outcome of the Iraq campaign. In the end, popular opposition to the war resulted in an American withdrawal.