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CALCULATING UNSEEN DANGERS

At the outset of Desert Storm, the U.S. Navy had plenty to worry about in Iraq’s high-tech arsenal. Saddam Hussein could launch Exocet missiles from Mirage fighters and Silkworm cruise missiles from land. But the most dangerous weapon threatening the U.S. fleet turned out to be one of the cheapest and least sophisticated: underwater mines. Mines had the potential to partially paralyze the Navy and would eventually blast two ships out of commission, injuring several sailors. So CNA field representatives supporting the naval forces were asked to calculate the risk to protect the mission — and save lives.

In the weeks before coalition forces began their attack to drive Iraq out of Kuwait, Admiral Stan Arthur, commander of coalition naval forces, wanted to move more of his fleet into the northern Persian Gulf, closer to Iraq and Kuwait. But that would bring them closer to concentrations of drifting mines. Unmoored and scattered by currents, Iraq’s drifting mines were an unnerving hazard for naval forces in the Gulf. All ships were on constant lookout, spotting as many as three a day across the fleet and sometimes dodging the mines at the last minute.

Adm. Arthur asked the CNA analysts with him aboard USS Blue Ridge, Dr. Marvin Pokrant and Dr. Ralph Passarelli, to calculate the risk and the effectiveness of various mitigation options. They used the discovery rate of drifting mines and current ship operating patterns to model the probabilities of a mine strike — with and without various countermeasures. The analysts concluded that if Navy ships operating in the northern Gulf took no countermeasures, there was about a 50-50 chance one of them would hit a floating mine in the next 30 days. The admiral didn’t like the odds.

But the analysts’ model also suggested that if ships cut their speed in half at night, that risk dropped by half. Helicopter searches at dusk of waters upcurrent from the ship would cut the risk in half again. So Admiral Arthur directed ships to transit at night at the slowest speed consistent with their mission, to keep watertight doors secured below deck, and to scout with helicopters at dusk. Within a couple of weeks, he felt sufficiently comfortable with the situation to move carrier strike groups to operating areas farther north. And no Navy ship was damaged by a drifting mine.

Even more mines were invisibly moored in an arc along the Kuwaiti coast, threatening a possible amphibious assault — and demanding more analysis. Before landing Marines on the coast of Kuwait, battleships and destroyers would need a week to prepare the assault area. And before that, minesweepers needed to make the waters offshore safe for those fire-support ships. But mine countermeasures planners were quantifying the options in terms of “percentage level of clearance,” which was not a metric the assault planners could use. Pokrant later wrote in Desert Storm at Sea: What the Navy Really Did, “What the operators wanted to know was whether they would strike a mine.”

Pokrant incorporated intelligence estimates for the density and distribution of mines and some assumptions about ship operations to convert those level-of-clearance estimates into a metric the assault planners could understand: probability that a ship would hit a mine. At a clearance level of 80%, which the minesweepers planned to reach in 18 days, he estimated a 40% probability that one of the seven battleships and destroyers would hit a mine in a week of operations. If mine clearance was sped up, stopping at a 60% clearance level, they would save five days of minesweeping, but with the likely result that one of the seven ships would strike a mine.

This analysis became instrumental in the planning for an amphibious assault. It also formed an important part of the briefing for General Norman Schwarzkopf that resulted in the commander’s decision against a full-scale amphibious assault — though mines were just one of many issues that figured into his decision.

Looking back, Pokrant says, “those were the best use of models in my entire CNA career; not because the models were sophisticated — they weren't — but because of the interaction with the operators.” He explains that the iterations between analyst and officers made both sides think more clearly. They forced the naval planners to focus on identifying their objective and their available assets to achieve that objective. And they forced the analyst to tailor the model to use the most appropriate data and answer the precise questions they wanted answered. The value of that interaction explains why CNA sent 22 Field Program analysts into the theater for Desert Shield and Desert Storm — and why CNA analysts have deployed in every major conflict involving U.S. troops since World War II.