Work is under way to make all men in Poland undergo military training, Prime Minister Donald Tusk said.
In a speech to the Polish parliament, Tusk said the government aimed to give full details in the coming months.
Efforts are being made to "prepare large-scale military training for every adult male in Poland," he told the Sejm.
"We will try to have a model ready by the end of this year so that every adult male in Poland is trained in the event of war, so that this reserve is comparable and adequate to the potential threats."
Tusk said the Ukrainian army has 800,000 soldiers, whilst Russia has around 1.3 million and he wants to increase the size of the Polish army, including reservists, to 500,000 from around 200,000 now.
"We're talking about the need to have an army of half a million in Poland, including the reservists," he said.
"It seems if we organise things wisely, and I'm talking constantly with the Minister of Defence, we will have to use several courses of action. That means the reservists, but also intensive training to make those who do not go into the army fully-fledged and competent soldiers during a conflict," he added.
Tusk said women may also undergo military training, but "war, is still to a greater extent the domain of men".
The prime minister said his government was also "carefully examining" France's proposal to include Europe under its nuclear umbrella.
"I would like to know first of all in detail what it means in terms of the authority over these weapons," he said.
Tusk pointed out Ukraine was invaded after it got rid of its own nuclear arsenal, adding Warsaw would like to acquire its own nuclear weapons, however remote a possibility that may be.
"Today, it is clear that we would be safer if we had our own nuclear arsenal, that is beyond doubt. In any case the road to that would be very long and there would have to be a consensus too," he said.
Poland is already planning to spend 4.7% of its economic output on defence this year, the highest proportion in the Nato alliance.
Tusk told parliament that spending should increase to 5% of GDP.
Earlier, President Duda proposed amending the constitution to make defence spending at a level of 4% of GDP compulsory
The prime minister also said he supports Poland withdrawing from the Ottawa convention that bans the use of antipersonnel landmines, and also possibly from the Dublin convention that bans the use of cluster munitions.
Poland has ramped up defence spending since Russia's full-scale invasion of neighbouring Ukraine in 2022.
It has signed arms contracts worth around $20bn (£15.5bn) with the United States to buy 250 M1A2 Abrams battle tanks, 32 F-35 jets, 96 Apache helicopters, Javelin missiles, and artillery rocket systems.
Warsaw has also signed contracts with South Korea to purchase K2 tanks and FA-50 light combat aircraft.
There is growing anxiety among Poles about their future security following US President Donald Trump's decision to suspend military supplies to Ukraine. Most Poles believe supporting Ukraine is in their own security interests.
Mirosław Kaznowski, the deputy mayor of Milanówek, a small town outside Warsaw, told BBC News this week that a friend of his has decided to invest in a start-up to build low-cost underground bomb shelters for businesses and homes.
His friend said interest was high, he added.
In a speech to the Polish parliament, Tusk said the government aimed to give full details in the coming months.
Efforts are being made to "prepare large-scale military training for every adult male in Poland," he told the Sejm.
"We will try to have a model ready by the end of this year so that every adult male in Poland is trained in the event of war, so that this reserve is comparable and adequate to the potential threats."
Tusk said the Ukrainian army has 800,000 soldiers, whilst Russia has around 1.3 million and he wants to increase the size of the Polish army, including reservists, to 500,000 from around 200,000 now.
"We're talking about the need to have an army of half a million in Poland, including the reservists," he said.
"It seems if we organise things wisely, and I'm talking constantly with the Minister of Defence, we will have to use several courses of action. That means the reservists, but also intensive training to make those who do not go into the army fully-fledged and competent soldiers during a conflict," he added.
Tusk said women may also undergo military training, but "war, is still to a greater extent the domain of men".
The prime minister said his government was also "carefully examining" France's proposal to include Europe under its nuclear umbrella.
"I would like to know first of all in detail what it means in terms of the authority over these weapons," he said.
Tusk pointed out Ukraine was invaded after it got rid of its own nuclear arsenal, adding Warsaw would like to acquire its own nuclear weapons, however remote a possibility that may be.
"Today, it is clear that we would be safer if we had our own nuclear arsenal, that is beyond doubt. In any case the road to that would be very long and there would have to be a consensus too," he said.
Poland is already planning to spend 4.7% of its economic output on defence this year, the highest proportion in the Nato alliance.
Tusk told parliament that spending should increase to 5% of GDP.
Earlier, President Duda proposed amending the constitution to make defence spending at a level of 4% of GDP compulsory
The prime minister also said he supports Poland withdrawing from the Ottawa convention that bans the use of antipersonnel landmines, and also possibly from the Dublin convention that bans the use of cluster munitions.
Poland has ramped up defence spending since Russia's full-scale invasion of neighbouring Ukraine in 2022.
It has signed arms contracts worth around $20bn (£15.5bn) with the United States to buy 250 M1A2 Abrams battle tanks, 32 F-35 jets, 96 Apache helicopters, Javelin missiles, and artillery rocket systems.
Warsaw has also signed contracts with South Korea to purchase K2 tanks and FA-50 light combat aircraft.
There is growing anxiety among Poles about their future security following US President Donald Trump's decision to suspend military supplies to Ukraine. Most Poles believe supporting Ukraine is in their own security interests.
Mirosław Kaznowski, the deputy mayor of Milanówek, a small town outside Warsaw, told BBC News this week that a friend of his has decided to invest in a start-up to build low-cost underground bomb shelters for businesses and homes.
His friend said interest was high, he added.
