Question: The 6th Canadian Infantry Division was originally scheduled to participate in this proposed Allied plan for the invasion of Japan near the end of World War II but the plan was abandoned after the Soviet invasion of which region? 

Context paragraphs:
7th Canadian Infantry Brigade: The 7th Canadian Infantry Brigade was an infantry brigade of the Canadian Army that fought during World War I and World War II.  The brigade, along with the 8th Canadian Infantry Brigade and the 9th Canadian Infantry Brigade, formed the 3rd Canadian Infantry Division.  The division was formed in late 1915 in France, and served on the Western Front until the armistice in November 1918.  Later, during World War II, it arrived in the United Kingdom in 1940 and spent three years in garrison duties and training in preparation for the assault landings on Juno Beach in Normandy on 6 June 1944.  After fighting in Normandy, the brigade took part in the Battle of the Scheldt.  After the war, it served on occupation duties until being disbanded in June 1946.

87th Battalion (Canadian Grenadier Guards), CEF: The 87th (Canadian Grenadier Guards) Battalion, CEF was a unit in the Canadian Expeditionary Force during the First World War.  Based in Montreal, Quebec, the unit began recruiting in September 1915 in Montreal, the surrounding districts, and also in mining districts elsewhere in the province.  After sailing to England in April 1916, the battalion was stationed there as part of the 12th Infantry Brigade (until June) and then 11th Infantry Brigade of the 4th Canadian Infantry Division until August of the same year.  On August 11/12, the battalion crossed over to France and served the duration of the war as part of the 11th Infantry Brigade, 4th Canadian Infantry Division.  The battalion returned to Canada in June 1919.

8th Canadian Infantry Brigade: The 8th Canadian Infantry Brigade was an infantry brigade of the Canadian Army that saw active service during World War I and World War II as part of the 3rd Canadian Infantry Division.  The brigade fought on the Western Front during World War I from December 1915 to November 1918, and in Normandy and north-west Europe in 1944–1945 during World War II.  It was a square formation of four infantry battalions during World War I, but was reduced to a triangular formation of three battalions during World War II.

Operation Downfall: Operation Downfall was the proposed Allied plan for the invasion of Japan near the end of World War II.  The planned operation was abandoned when Japan surrendered following the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war and the Soviet invasion of Manchuria.  The operation had two parts: Operations Olympic and Coronet.  Set to begin in November 1945, Operation Olympic was intended to capture the southern third of the southernmost main Japanese island, Kyūshū, with the recently captured island of Okinawa to be used as a staging area.  Later, in the spring of 1946, Operation Coronet was the planned invasion of the Kantō Plain, near Tokyo, on the Japanese island of Honshu.  Airbases on Kyūshū captured in Operation Olympic would allow land-based air support for Operation Coronet.  If Downfall had taken place, it would have been the largest amphibious operation in history.

9th Canadian Infantry Brigade: The 9th Canadian Infantry Brigade was an infantry brigade of the Canadian Army that saw active service during World War I and World War II as part of the 3rd Canadian Infantry Division.  The brigade fought on the Western Front during World War I from January 1916 to November 1918, and in Normandy and north-west Europe in 1944–1945 during World War II.  It was a square formation of four infantry battalions during World War I, but was reduced to a triangular formation of three battalions during World War II.

4th Canadian Division: The 4th Canadian Division is a formation of the Canadian Army.  The division was first created as a formation of the Canadian Corps during the First World War.  During the Second World War the division was reactivated as the 4th Canadian Infantry Division in 1941 and then converted to armour and redesignated as the 4th Canadian (Armoured) Division.  Beginning in 1916 the division adopted a distinctive green-coloured formation patch as its insignia.  In 2013 it was announced that Land Force Central Area would be redesignated 4th Canadian Division.  It is currently responsible for Canadian Army operations in the Canadian province of Ontario and is headquartered at Denison Armoury.

6th Canadian Infantry Division: The 6th Canadian Infantry Division was an infantry division of the Canadian Army, formed in 1942 during the Second World War.  It was attached to Pacific Command.  The division had a brigade sent to the Aleutian Islands Campaign, particularly at Kiska, but never saw action.  The 6th Division was to have been part of a proposed Commonwealth Corps, formed for a planned invasion of Japan, but was disbanded in 1945, after the war was ended by the bombing of Hiroshima and Nagasaki.

Operation Atlantic: Operation Atlantic (18–21 July 1944) was a Canadian offensive during the Battle of Normandy in the Second World War.  The offensive, launched in conjunction with Operation Goodwood by the Second Army, was part of operations to seize the French city of Caen and vicinity from German forces.  It was initially successful, with gains made on the flanks of the Orne River near Saint-André-sur-Orne but an attack by the 4th and 6th Canadian Infantry Brigades of the 2nd Canadian Infantry Division, against strongly defended German positions on Verrières Ridge to the south was a costly failure.

8th Canadian Infantry Division: The 8th Canadian Infantry Division was a Canadian formation that served within Pacific Command in Western Canada during World War II.  The Division units were raised on 18 March 1942 and the HQ was raised on 12 May 1942 at Prince George, BC.  The Division was a home defence unit.  It initially consisted of the 19th, 20th, and 21st Canadian Infantry Brigades.  In July the home Defence Divisions were reorganised and the 8th Division consisted of the 14th and 16th Infantry Brigades.  The 19th Brigade went to the 6th Canadian Infantry Division, the 20th went to the 7th Canadian Infantry Division, and the 21st would remain at Valcartier, PQ as a strategic reserve.  The 8th Canadian Infantry Division was disbanded on 15 October 1943, along with the 16th Brigade.  The 14th Brigade returned to the 6th Division.

Battle of Le Mesnil-Patry: The Battle of Le Mesnil-Patry during the Second World War, was the last attack by an armoured battle group conducted by Canadian troops in Normandy in June 1944.  The Queen's Own Rifles of Canada of the 8th Canadian Infantry Brigade of the 3rd Canadian Division, supported by the 6th Canadian Armoured Regiment (1st Hussars) of the 2nd Canadian Armoured Brigade attacked the village of Le Mesnil-Patry in Normandy, to advance southwards towards the higher ground of Hill 107 to the west of Cheux.  The attack was intended to support a larger operation by the 50th (Northumbrian) Infantry Division and the 7th Armoured Division to capture the city of Caen and to advance in the centre of the bridgehead next to the First US Army.  The battle was a German defensive success but the greater German objective of defeating the invasion by a counter-offensive also failed.

Supporting paragraphs: 6th Canadian Infantry Division Operation Downfall
Answer: Manchuria