On Anzac Day thoughts turn to those who gave their lives during various wars over the last century. But there is one group which has never been given recognition for what they achieved in World War II and that is the United States submariners, 3505 of whom lost their lives, including 374 officers.

When one analyses what they achieved there is no doubt they did more than any other group to defeat the Japanese and save Australia and New Zealand from being invaded.

The reason is simple - they sank more than 60 per cent of the Japanese merchant marine fleet. Without these ships, not only was the Japanese advance stifled, their occupying troops lost their supply lines and they virtually could not be evacuated like the British were at Dunkirk to fight in other battles.

Additionally with the loss of shipping, Japan found it very difficult to supply the home land with raw materials from the conquered territories.

After the Japanese invasion of Manchuria, the US instigated a policy of restricting supplies to Japan. This ultimately led to the Japanese attack at Pearl Harbour on December 7, 1941.

The Japanese advance over the next five months was nothing short of staggering _ Hong Kong, the Philippines, Burma, Borneo, Malaya, Thailand, Indo-China (Laos, Cambodia and Vietnam) and Singapore on February 15, 1942 where 80,000 troops surrendered (the largest surrender of British military personnel in history) were occupied. Ships played a most important part in this role.

The Dutch East Indies (Indonesia ) was occupied in March and Darwin first bombed on February 15, 1942. The farthest Japanese advance was Guadacanal in the Solomon Islands by July 6. The farthest advance in Burma was on May 8, 1942, which was the second day of the Coral Sea battle - their first setback, followed by the Battle of Midway on June 3-6.

Without a huge marine fleet this advance would never have been possible. Over the next two years the US Navy submarine fleet went to work.

Fortunately they had cracked the Japanese naval code so they virtually knew their every move. The Japanese had also failed to destroy the enormous naval fuel-oil installations at Pearl Harbour when Admiral Nagumo did not go ahead with the third wave of air strikes.

Admiral Nimitz, Commander in Chief of the US Navy Pacific Fleet, said that had the tanks been destroyed the war would have been prolonged by two years as it would have immobilised every ship in the Pacific Fleet.

The Japanese had no long-range anti-submarine aircraft and probably their destroyers were not that well equipped to deal with submarines. The problem for the American Navy was where to base the submarines. Darwin was ruled out because the harbour was considered too shallow. Finally Fremantle (near Perth) was chosen and obviously that was too far away for the Japanese to attack with aircraft. It was a long haul for the submarines to the areas where Japanese ships were active to the north but on the surface, diesel-powered submarines have a tremendous range.

Obviously they would sail on the surface for most of their operations to and from Fremantle. Evidently Japan never found out where the submarines were based. The Fremantle base had 125 American, 31 British and 11 Free Dutch submarines. The Americans deployed 288 submarines during the war so nearly half operated from the Fremantle base.

Japan started the war with six million tonnes of shipping and of course built more as the war went on. US submarines sank 1314 of their ships of more than 1000 tons each, plus 700,000 tons of naval ships including eight aircraft carriers, a battleship and 11 cruisers.

They did 416 patrols and fired 14,500 torpedoes. Out of a total of 52 subs lost, 48 were lost operating from the Fremantle base. American submariners made up only 1.6 per cent of the US naval manpower but they had the highest loss rate of US Armed Forces with 22 per cent killed.

At the German Naval Museum at Laboe, northeast of Kiel, there is a memorial to the 3505 American submariners and a memorial to the 31,000 German submariners who lost their lives out of a total of 39,000 men who served in their U-boats. The Germans built 1154 U-boats and lost 800.

More than 50,000 allied Merchant Seamen lost their lives, many as a result of U-boat activity. They, too, have never been given true recognition for what they achieved in the Atlantic and the sacrifices they made.

Last year while in Los Angeles I spoke to a group of American submariners. Many did not know of their predecessors' achievements in the war and none knew there was a base in Fremantle.

They are going to make a concerted effort to bring this oversight into prominence when remembrances are held. Their sacrifices certainly saved us from invasion.

Anzac Day is now also the time to remember those 3505 dead submariners of the US Navy.