Boston — A smokescreen was an effective tactic in World War I naval warfare. Stacks piped out dark clouds of smoke to cover valuable ships, making it difficult for an enemy to target them.
The current debate over how many ships should comprise the US Navy (going to 600 from its present 450) may inadvertently be doing the same to the Navy's commercial counterpart, the US merchant marine.
A strong merchant marine contributes to a nation's sealift capability - the amount of men and materials deliverable by sea under naval protection on a military mission. It plays a vital role in national defense.
Secretary of the Navy John Lehman in a telephone interview told the Monitor that ''95 percent of any bulk logistics (war fighting material) to support a military operation must move by sea.''
After the Soviet invasion of Afghanistan, President Carter's Mideast policy faced a sealift shortage. The much touted Rapid Deployment Force did not have the kind or number of ships needed to respond to a military crisis in the Persian Gulf. The sea lanes of the West's vital oil-supply line were seen as vulnerable.
As one wag put it, ''In a Persian Gulf conflict, the Soviets drive to work, while we have an 8,000-mile nautical fire hose to string.''
The American philosopher of sea power, Alfred Thayer Mahan, long ago summarized the problem of control of the seas in a simple formula: ''Navy, plus bases, plus merchant marine, equals sea power.'' According to Admiral Mahan, ''A navy without a strong merchant marine is like a (plant) which, having no root, soon withers away.''
Comparative measures show the Soviet Union has cultivated, while the US has let wither, the merchant roots of its naval forces.
Secretary Lehman sees as a critical national problem the fact that ''there are more Soviet . . . than American ships operating in this country's foreign trade.''
Twenty-five percent of all regularly scheduled transatlantic European and Mediterranean cargo traffic originating in the United States is carried in Russian ships. Twenty-three percent of all liner cargo originating in the Great Lakes for European or Mediterranean ports goes in Soviet bottoms.
''The fourfold increase in Soviet merchant ships in 17 years results from national policies that create shipbuilding capabilities, strong maritime markets , a pool of trained seamen, and ships,'' says Gil Slonim, president of the Oceanic Education Foundation in Falls Church, Va. ''The figures for the US indicate an absence of policy.''
''A peacetime merchant marine can keep sea lanes open, crews updated in technological improvements, and ensure an immediate backup for military purposes ,'' says Mr. Slonim.
Of high priority to Secretary Lehman is that ''a national maritime policy must be developed. Some formula has to be achieved with numerous other government agencies and departments and we are marching off to do this.''
The Transportation Department's Committee on Merchant Marine and Fisheries in a report to Congress stated any NATO resupply could be handled by the combined NATO merchant fleets. In a NATO confrontation, materials already on hand in Europe are adequate for at most 30 days.
But an Achilles' heel is dependence on sophisticated container ships and the automated terminals of European ports. If these facilities are destroyed, the ships can't unload.
Demonstrating a shift in emphasis, the centrally coordinated Soviet merchant fleet gives much greater weight to operating independent of the more industrialized ports.
Soviet policy dictates that roll-on roll-off ships (ships that carry their own on- and off-loading ramps) comprise a larger percent of the Soviet merchant fleet. This gives greater commercial and military access to less developed nations.When a non-NATO operation in the third world is contemplated ''Bulk tonnage substantially exceeds what we are likely to have in the way of ships for the forseeable future,'' says Mr. Lehman. How does the US obtain a better mix of ships to meet both commercial and military needs? Mr. Lehman emphasizes ''the current Navy shipbuilding program seeks to do this by keeping the industry alive and healthy. The industry is depending on Navy ships to get it through difficult times.''By carrying third-world trade, a merchant fleet makes possible clandestine arms shipments to favored allies. The Cuban missile crisis occurred when aerial photos revealed Soviet merchant vessels carrying missiles. Modern container ships would escape such aerial detection.In the electronic age, a global merchant fleet is capable of monitoring combat ships as well as surveillance of port facilities.Jim Mulquin, project coordinator for the US Navy's ARAPAHO program, an effort to put antisubmarine equipment on commercial container ships, says, ''It is widely known that Soviet merchant ships carry more extensive communications than is required for normal merchant operations, and it is also well known that they carry additional staff, equipment, and electronic gear that are very useful in the collection of intelligence.'' Armed merchant ships can interrupt the traffic of opposing merchant fleets unless these fleets are escorted. This threat ties up naval ships in missions other than combat ones. Merchant ships, or a fishing fleet rendezvousing with naval vessels, can serve as decoys to precision guided munitions or satellite surveillance systems. A proliferation of the numbers of potential targets may result in missiles wasted on merchant ships rather than combat ships. In an outbreak of hostilities, merchant ships could make modern mine laying ubiquitous. Virtually any ship can be used for mining operations, and container ships whose cargo includes crated mines would be impossible to detect. Strategic ''choke points,'' narrow sea passages connecting various oceans, (e.g. the Strait of Hormuz in the Persian Gulf, the Gulf of Aqaba and Bab al Mandab in the Red Sea, the Panama and Suez Canals, the Strait of Malacca in Indonesia) are particularly vulnerable to mine laying. With oil moving through a maritime pipeline to the Western democracies, curtailment of tanker traffic by blockage of choke points, or at least the threat of such action, becomes both a diplomatic as well as a military option. Statistics compiled by the Shipbuilders Council and the US Department of Transportation's Maritime Administration show the Soviet international commercial fleet at 2,530 ships, up some 2,000 from the 1960 level of 590 ships.This does not include the Soviet fishing fleet, largest of its kind in the world. More than 550 factory ships support 4,000 fishing vessels.In 1940 the US oceangoing merchant fleet comprised nearly 1,400 ships and grew to more than 5,000 during World War II. As of July 1, 1981, the US merchant fleet was down to 722 deep-draft ships despite a geometric rise in world commerce and international oil shipments. Of these, 578 are oceangoing ships and 144 ply the Great Lakes.As Alfred Thayer Mahan never tired of pointing out, maritime forces or their lack, dictate the outcome of land battles. One telling example is when the Carthaginian general, Hannibal, crossed the Alps into Italy with a contingent of elephants and unsuccessfully attacked Roman forces. Rome controlled the sea around the Mediterranean and Hannibal and his elelphants faced starvation if they remained in Spain. The crossing of the Alps, rather than being the brilliant strategy of history's first ''armored'' division , in fact was a tactic of desperation. His men and few elephants arrived exhausted and were easily defeated.