Police seized 12kg of "high purity cocaine" equivalent to 48kg of "cut cocaine" worth between £1.5m and £4.5m.
Cardiff Crown Court heard at least 36kg of mephedrone worth up to £300,000 was also seized.
Eleven of the 13 defendants from Blaenau Gwent, Newport and Rhondda Cynon Taff were jailed for drugs offences.
Ashley Burgham, 28, from Blaina was described as the head of the organisation with Michael Barnes, 32, from Abertillery, as his second in command who met national suppliers.
Others were couriers who supplied "downstream customers" and met suppliers.
Gwent Police also seized £205,494 in cash during the operation.
Originally, the gang met an Albanian crime group to get hold of drugs, but when this relationship ended, they turned to a supplier in Spain.
Det Chf Insp Roger Fortey said: "Officers carried out a meticulous enquiry to dismantle this sophisticated organised crime group.
"The defendants in this case were motivated by greed and profits and had convinced themselves that they were untouchable."

Defence attaché Capt Oleg Kornienko presented Ushakov medals to the men of the Arctic Convoys.
Able seaman Charles Lewis, 91, from Calmore, Hampshire said he was "honoured and delighted".
The Foreign Office initially did not allow Russia to honour the veterans as it broke the rules on foreign medals.
The Russian embassy said the convoys allowed Russian soldiers to defeat the Germans on the Eastern Front.
Mr Lewis said: "I certainly don't see myself as a hero - far from it - and I think all my friends and colleagues, many of whom sadly are no longer with us, would regard us as simply doing our bit for the war effort.
"Although I have to say that Churchill's famous quote about the Arctic convoys' missions through the North Sea in winter as being 'the worst journey on earth' did strike a chord  - then and now."
•They consisted of vessels which travelled from Britain to northern Russia to resupply the Soviet Union during World War II
•Under constant threat of attack by German U-boats and aircraft, the craft also had to deal with severe cold, storms, and ice floes
•By May 1945, the Arctic route had claimed 104 merchant and 16 military vessels. Thousands of Allied seamen lost their lives
Source: National Maritime Museum
Minister-Councillor Alexander Kramarenko from the Russian Embassy said: "It [the ceremony] is done for them because they have been expecting for a very long time to be recognized.
"It is done for us as it was important for us.
"The arctic convoy was a material expression of our wartime alliance and they provided weapons and ammunition that armed us to defeat the Germans on the Eastern front.
"We and Britain were in it together."
More than 3,000 men died during the maritime campaign that Winston Churchill was said to have called the "worst journey in the world".
The Russian Embassy wrote to survivors in May 2012 that it intended to award them with the Medal of Ushakov as a symbol of the country's gratitude.
But the move was blocked by the Foreign Office as its rules stated British soldiers could not receive a foreign medal if the act happened more than five years ago.
The British Government created the Arctic Star in 2012 following a long campaign for the convoy veterans to be recognised.
But campaigners believed veterans should still be able to receive the Russian accolade.
The Foreign Office allowed an "exception to the rules" last year and President Vladimir Putin presented the first medals during his visit to London on 16 June 2013.
The Ushakov medal is awarded to sailors who have displayed courage in the course of defending Russia or its interests.
Members of an organised crime gang who plotted to supply millions of pounds worth of drugs have been jailed.
[NEXT_CONCEPT]
The Russian embassy has honoured 30 World War Two veterans in Southampton for their part in transporting crucial supplies to Russia.