Ceremonies to mark the creation of a single Scottish Army regiment have been held across the UK and elsewhere.
Soldiers received their new hats in a ceremony at Edinburgh Castle
The old six infantry regiments have become battalions of the new Royal Regiment of Scotland (RRS).
Major General Euan Loudon, the General Officer commanding the Army in Scotland, led the re-badging ceremony at Edinburgh Castle.
He told onlookers that it marked the start of a new chapter in the story of the Scottish soldier.
Maj Gen Loudon said: "Change may be painful but it has come to visit us in our day and generation and it follows on from a remarkable record of service in the antecedence regiments.
"This new regiment of ours will take time to establish its own personality, but those of us who have experienced change before know that it will do so with rightly placed confidence."
He added: "What we are not going to do, as we move forward into this new era is to create an amorphous mass, abandon the regimental system, or see these changes in terms of winners and losers."
The Royal Highland Fusiliers, the Black Watch, The Highlanders and The Argyll and Sutherland Highlanders form four battalions of the new regiment.
Later this year the King's Own Scottish Borderers and the Royal Scots will merge to form the 1st battalion RRS.
The Ministry of Defence said the restructuring will ensure 21st Century military commitments can be met.
Opponents have argued it could weaken recruitment while the Tories have branded the move "dangerous" cost cutting.
The new insignia of the Royal Regiment of Scotland
The Scottish National Party said it was a sad day for all who had fought to save Scotland's historic regiments.
In Scotland, the main parade and re-badging ceremony took place at Edinburgh Castle.
Maj Gen Loudon presented the new headdress to representatives from the battalions.
The KOSB and Black Watch held ceremonies in Northern Ireland, while The Argyll and Sutherland Highlanders marked the event in Canterbury, Kent.
Around the world, formation parades also took place in Iraq for The Royal Scots and The Highlanders and in Cyprus for The Royal Highland Fusiliers.
Territorial Army units around Scotland will hold their re-badging ceremonies at drill nights starting from Tuesday.
Jeff Duncan, spokesman for the Save the Scottish Regiments Campaign, said Scotland was losing something very important for no good reason.
He added: "The Labour government have betrayed the regimental brotherhood for the sake of saving money. And that's what's so despicable."
SNP MP Pete Wishart said: "These regiments served us with such distinction for centuries and have been effectively abolished with a stroke of a pen."