It's called the longest and deadliest war in US history - the war on drugs.

It's cost billions of dollars and thousands of lives.

On Monday a Caravan For Peace arrived in Washington DC after travelling across 13 states, calling the US and Mexico governments' policy a failure and campaigning for drug law reform.

On board was poet Javier Sicilia, whose innocent son was killed by a drug cartel in Mexico.

"Seventy thousand people have lost their lives in this war, 20,000 people have been disappeared, two hundred and 50,000 have been displaced ... this war has done more damage to our people than addiction itself".

At the wrong time

Also travelling with the Caravan For Peace was Teresa Carmona, whose son Joaquin was killed in Mexico City. That's all she knows because the police will only say he was in the wrong place at the wrong time.

"There is no investigation whatsoever you know. After 25 months I'm still hoping that Joaquin receives justice."

There's been a War on Drugs since the 1970s when President Richard Nixon was the first to coin the phrase.

The first national policy chief - the so-called Drugs Czar - was appointed in the early 1980s by Ronald Reagan.

Insatiable demand

The US is committing $25bn in 2012 to the War on Drugs but the evidence suggests that, over 30 years, insatiable demand has only boosted supplies, reduced prices and sparked armed conflict among gangs in the US and especially in Mexico, where cartels control 90% of the illicit drugs that enter the US.

It's a mostly federal policy. States spend heavily too, pushing the price tag closer to $50bn that encompasses more than just drugs - gun smuggling, money laundering, and immigration are involved.

Some people say the policy is on autopilot.

The US is pretty much alone in the War on Drugs with the exception of Mexico. 

The Swedes are pretty tough and the French sometimes crack down, but large swathes of Western Europe, Australia and Canada are not as draconian as the US, which locks up more people than anyone else for drugs offences.

Peter Reuter, from the University of Maryland, told me he would not say the War on Drugs is a failure but he agrees it's sometimes hard to see its success.

On autopilot

Reuter says too many people are being locked up for drugs offences and that's because the programme's been on autopilot for years.

"Nobody is making decisions about this," he says. "US attorneys continue to prosecute large numbers of people for quite minor participation in drug importing."

At the Caravan, they are in favour of legalising drugs and regulating their distribution - just like alcohol.

Neill Franklin, a former law officer, who now runs Law Enforcement Against Prohibition says clear-blue thinking is required because, despite all the cash that's been spent over the years, drugs appear to be here to stay.

"I don't think it's a tall order at all ... it's just getting the information to the people so they can make our leaders, the politicians change our policies"

That's unlikely to be soon ... the issue of drugs hasn't so far cropped up in this year's presidential election campaign.