In the early hours of March 20, 2003, British soldiers, sailors and airmen joined U.S. forces in the invasion of Iraq and the toppling of Saddam Hussein. Thus far, they have played a vital role in rebuilding Basra and the critical Persian Gulf port of Umm Qasr. Massive shipments of military materiel were essential to their success, and basically, anything that wasn’t a vehicle, live ammunition or fresh provisions (which have different supply lines) began its journey to the Gulf from England’s military warehouses. In the few weeks prior to the invasion of Iraq, these depots sent by ship or air 3,169 20-foot shipping containers to the Gulf, along with almost 22,000 3-foot pallets.

Getting these shipments to the Gulf was a logistical nightmare that would have been far more fraught had the British defense ministry not embarked four years ago on a $10.8 million effort to pull together three separate supply chains: This involved reconciling some 850 different information systems, and integrating three inventory management systems and 15 remote systems.

The biggest foe in this massive integration effort was not Saddam Hussein, but dirty or disparate data. To one system, stock number 99 000 1111 was a 24-hour, cold-climate ration pack. To another system, the same number referred to an electronic radio valve. And if hungry troops were sent radio valves instead of rations, the invasion and rebuilding of Iraq wouldn’t have gone very far.

Dirty data has long been a CIO’s bugbear. But in today’s wired world, the costs and consequences of inaccurate information are rising exponentially. Muddled mailing lists are one thing, missing military materiel quite another. Throw in the complications arising from merging different data sets, as in the aftermath of a merger or acquisition, and the difficulties of data cleansing multiply. For this article, we interviewed seasoned data-cleaning veterans from organizations as diverse as the British Ministry of Defence, the U.S. Census Bureau and Cendant, a real estate and hospitality conglomerate. But the lessons learned contain two common themes: How to surmount the technical challenges of cleaning data, and how to align IT staff with the business side to ensure that the task gets done right.

Know Your Enemy

When Britain’s defense department began its data-cleaning project in early 2000, it faced a huge task, says Lt. Col. Andrew Law, head of The Cleansing Project. (It just so happens that the acronym TCP is also a well-known British brand of antiseptic.) The department’s IT team was using three main systems to sort through 1.7 million records, which each had literally hundreds of attributes. Each record referred to an item that troops might require, and many of these items were to be dispatched from the ministry’s widely dispersed warehouses in Bicester, England, and other locations. (The Bicester warehouses are far apart because they were built in 1942 with the idea to make it hard for German bombers to deliver a knockout punch.)