Letters on the occasion were sent by President Andrzej Duda and PM Mateusz Morawiecki.
In his letter, Duda reminded that Szczecin was one of the main sites of the 1980 protests, and stressed that the August Agreements laid the foundation for a free Polish state.
"August 1980 is the founding-block of free Poland, at the same time it was a historical breakthrough which gave the beginning to major changes that transformed Europe and the world," Duda wrote.
Duda added that the struggle undertaken by the Poles at the time inspired other nations, as the protesters "rose against the evil of the communist system to fight for dignity, freedom and truth."
He also pointed out that the ethos of August 1980 constituted "a living inspiration for the future," and admonished that the betrayal of those ideals was tantamount to "endanger the foundations of a free, strong and just Republic."
In his letter, Morawiecki recalled that August 1980 was a breakthrough which led to the formation of the Solidarity Union.
"The August 1980 freedom upsurge was a great historical moment. A spark that ignited the flame of freedom," Morawiecki wrote, adding that the August events resulted in changes that "led Poland to the fall of communism and Europe to the collapse of the Soviet empire."
The PM also observed that August 1980 was formative for the identity of Szczecin, which at the time was the second-largest centre of protest alongside Gdansk.
"The people of August were soldiers in a relay race to freedom for which today's free Poland owes eternal gratitude," Morawiecki wrote, adding that "the great idea of solidarity must be proudly handed over the next generations."
A special commemorative mass on the occasion was attended by former Szczecin shipyarders, oppositionists, unionists, parliamentarians, local authorities, government officials and members of the uniformed services.
Sealed on August 31, 1980, the August Agreements were an accord between the rising Solidarity Union and Poland's communist authorities. They were signed in the wake of worker strikes in Gdansk and other Baltic coast locations earlier that month. The agreements contained the famous "21 postulates," which among others led to the legalisation of Solidarity. (PAP)