Senior figures in the Orange Order have described Scottish nationalism as "a divisive and evil enemy".
Thousands of Orangemen held a "Proud to be British" rally in Edinburgh in support of the Union.
They gathered in the Meadows to hear speeches by grand masters and senior figures from around the UK, before setting off past some of Edinburgh's most famous landmarks including the former house of their inspiration John Knox and the General Assembly Hall where his statue stands.
They also passed the Scottish Parliament and the Palace of Holyroodhouse, as supporters lined the streets to cheer them on and cry "No" to Scottish independence.
In a speech ahead of the march, Grand Chaplain Henry Williamson said: "Brothers and sisters, in a world of instability, a world of insecurity, a world of nuclear proliferation, of radical Islam, people look to the UK as a land of hope, a land of peace, of success and unity and an example if what they so desperately long for - unity not stupidity, unity not division, unity not separation, unity not them and us.
He added: "Let me remind you that when an enemy came against the city of Londonderry, God's people famously said there will be no surrender to this evil enemy.
"It was a cry we made in 1914, it was a cry we made in 1939, it is a cry British people make every time we face an enemy who seek to destroy who and what we are, and a cry that we make on behalf of the underdog.
"Well, a divisive and evil enemy has arisen against Scotland in the guise of false patriotism and the nationalist referendum, against our beloved United Kingdom, and our reply as God's people this time is 'no separation'."
Ron Bather, grand master of the Grand Orange Lodge of England and imperial grand Master of the Imperial World Council, said: "As individual nations, could we have succeeded in defeating Nazism in 1939? I don't think so.
"It was the resolve and the endeavour of the individuals that make up this country that stood up against a mightier foe, and how many times in the past has this country been left to stand alone and yet has never been defeated.
"To you Scottish sisters and brethren, this coming week is you chance to defeat once and for all the separatists, the people that want to change your way of life."
He added: "Over that last few days, certain people in the No camp have been questioning the validity of taking to the streets of Edinburgh today.
"Let me say to them people, as members of the Orange Institution we don't sit behind closed doors and plan things, we don't walk the streets with balaclavas on, we walk the streets openly to profess our religion and our heritage."
Edward Stevenson, grand master of the Grand Orange Lodge of Ireland, said: "Next year, as is a long held tradition, many of us will come over to Scotland for the annual Battle of the Boyne commemorations, and we very much hope that we will not require our passports."
Police Scotland later said the march passed peacefully with no arrests.
Around 15,000 participants and 110 Orange Lodge bands took part and several thousand spectators turned out to watch the event, police said.
Superintendent Phil O'Kane said: "We would like to express our sincere thanks to the public for their co-operation during what was a peaceful march."