Anzac Day is Australia's most solemn moment each year.

This week we will again remember those who served with courage and purpose, and honour those who paid the ultimate price for defending our nation.

It is fitting, given how many Australian towns were emptied of their young men, that on Anzac Day, among the bugles and slouch hats, our minds turn to the sacrifice of those enlisted at Gallipoli and other subsequent wars.

In Australia, until World War II, women wanting to serve their country were restricted to nursing and we have seen the images of those incredible women in makeshift hospitals, tending injured soldiers. Today, women make up 21 per cent of serving ADF members.

The contribution of women in Allied countries during World War II is underestimated. We may know of those who have been immortalised on screen like New Zealand-born and Sydney-raised French resistance fighter Nancy Wake, or have seen images of then-Princess Elizabeth in overalls as a mechanic in the Auxiliary Territorial Service.

But I want to talk about two women, one Irish and one Australian, whose names you probably won't know, and whose actions helped change the course of World War II.

I'll start with Maureen Flavin (later Sweeney), a young Irish woman who in 1942 took a job at a post office in the coastal village of Blacksod Point, the westernmost point of Ireland.

The Blacksod Point post office was also a weather station and Maureen's duties included recording and transmitting weather data.

What Maureen didn't know was that, despite Ireland being neutral in World War II, her weather reports were aiding the Allies.

Blacksod was perfectly positioned to get an early indication of the weather headed towards Europe.

Maureen's weather report was integral to the D-Day operation that changed the course of WWII.

The landings at Normandy, the largest seaborne invasion in history, were bloody with steep casualties but ultimately led to the defeat of nazi Germany.

Under the leadership of US general Dwight D. Eisenhower, 160,000 troops, including thousands of Australian airmen and soldiers, nearly 12,000 aircraft and nearly 7000 sea vessels were due to land on an 80km stretch of beach along the French coast to begin the liberation of Western Europe.

After two years of planning, the date of June 5, 1944, was chosen for the full moon and low tide that would allow good visibility and accessibility.

Clear skies and calm seas were crucial.

Cue Maureen Flavin. On June 3, her 21st birthday, Maureen saw the barometer dropping and reported that stormy weather was approaching. Unusually, Maureen received a series of calls, asking her to repeat her assessment.

She enlisted the postmistress' son, Blacksod's lighthouse keeper and the man she would marry, Ted Sweeney, to be a second set of eyes. Ted confirmed she was right the first time.

Based on Maureen's report, Gen. Eisenhower postponed the invasion. Had he not, the military operation would have been disastrous - a mix of rough seas, thick cloud, and high winds.

Not only did Maureen Flavin have the power to stop an invasion on June 5, but she was confident in her forecast that the next day would be better.

The Germans were forecasting that gale force winds and rough seas would deter any Allied invasion. As a result, the nazis redeployed crucial Panzer divisions away from the coast and German Field Marshall Erwin Rommel, aka the Desert Fox, even returned home for his wife's birthday. But it was Maureen Flavin - not the nazi war machine - who was right.

And, sure enough, on June 6 the skies cleared.

Postponing any longer would have meant a delay of weeks, waiting for the next full moon and favourable tide and losing the element of surprise. Had that been the case, victory in Europe might have been delayed by at least a year.

Here in Australia, there was another young woman who played an important role in shortening the war in the Pacific. Dorothy Hilleard (later Morrow) was just 19 years old when she joined the Australian Women's Army Service as one of 24 women in the Special Intelligence Service.

The SIS was part of US commander-in-chief Gen. Douglas MacArthur's Central Bureau. It was housed in a sprawling mansion called Nyrambla, at 21 Henry Street, Ascot, in Brisbane.

Henry Street was the southern hemisphere Allies' equivalent of England's famous Bletchley Park, where Alan Turing broke the nazi Enigma Code. In the Pacific, the SIS worked to crack the Japanese Kana Code. And they did, with great success.

And while Maureen Flavin was unaware of the role her weather reports played in the war until the 50th anniversary of D-Day,

Dorothy Hilleard knew that what she was doing was of nationally significant importance. The thing was, she was not allowed to tell anybody.

A plaque at Henry Street that honours the men and women of Central Bureau reads “Their strength lay in silence”.

Even Dorothy's own family and closest friends only discovered a few years ago that their sister, mother, aunty, friend was not “just a clerk”.

So closely did the members of the SIS guard the secret that the husband of one of the women died thinking she was a cleaner.

This veil of secrecy led to Dorothy's beloved brother, Bill, who was stationed in Papua New Guinea during the war, giving her a ribbing about only working for the Americans to take advantage of their endless supply of chocolates and nylon stockings.

Little did Bill know his sister's “admin” work included travelling with intelligence officers across Brisbane to take decoded information to Gen. MacArthur.

Messages intercepted by the Allies in 1943, including the US and Australian code crackers at Henry Street, were deciphered to reveal Admiral Isoroku Yamamoto's itinerary for a visit to the South Pacific. This allowed US Air Force fighter aircraft to shoot down his plane near Bougainville Island.

Admiral Yamamoto was the genius commander-in-chief of the Japanese Imperial Navy's Combined Fleet during the Battle of Midway and the attack on Pearl Harbor and his death shortened the conflict in the Pacific by an estimated two years, saving countless lives.

We lost both Dorothy and Maureen last year, 102 and 100 years old respectively. By chance, they died within two days of each other, Maureen on December 17 and Dorothy on December 19.

Each Anzac Day we lament the loss of the greatest generation and stories like Maureen's and Dorothy's are they reason why.

Women who humbly went about the business of winning the war - one unwittingly, the other silently. But both with diligence and pride and never seeking glory. Unsung heroes.

And for every Maureen and Dorothy, there were thousands of other women around the world using their intellect, courage and tenacity to support the war effort. Their stories may just not have been discovered or told yet.

We need to tell them.

This opinion piece was first published in The West Australian on Wednesday 24 April 2024.