In September 1940 Thomas, by now a temporary brigadier, became Commander Royal Artillery (CRA) of the 2nd Infantry Division, which had recently fought in France with the British Expeditionary Force (BEF) and was then commanded by Major General Noel Irwin before being succeeded by Major General Daril Watson, both of whom had been fellow students at the Staff College, Camberley in the mid-1920s.

Thomas remained in this post until March 1942, when he was promoted to the acting rank of major general and became General Officer Commanding (GOC) of the 43rd (Wessex) Infantry Division, his first time in charge of a large formation of infantry, succeeding Major General Charles Allfrey, another artilleryman.
The 43rd Division – composed of the 128th, 129th and 130th Infantry Brigades, along with supporting divisional troops – was a first line TA formation recruiting from the West Country, serving in Kent on anti-invasion duties as part of XII Corps, under Lieutenant General James Gammell, who was replaced in November by Lieutenant General Montagu Stopford who, the following November, was himself replaced by Lieutenant General Neil Ritchie.

In June 1942, three months after Thomas became GOC, the 43rd Division was one of many selected to be converted into a "mixed" division, of one tank brigade and two infantry brigades.
As a result, Brigadier Manley James's 128th Brigade left the division and was replaced by the 25th Tank Brigade which, in September, was replaced by the 34th Tank Brigade.
Two months later, on 11 November, Thomas was promoted to the permanent rank of major general.
In September 1943, however, the experiment with "mixed" divisions was abandoned and, with the arrival of Brigadier Hubert Essame's 214th Infantry Brigade, formerly an independent unit, the division reverted to being a standard infantry division.
By this time Thomas's division had been selected to participate in the Allied invasion of Normandy, then scheduled to take place in May 1944, as part of the newly formed British Second Army (initially under Lieutenant General Sir Kenneth Anderson but later replaced in January 1944 by Lieutenant General Miles Dempsey), and training in all-arms co-operation, already at a very high standard due to Thomas's energetic and ruthless methods, intensified, and he demanded only the very highest standards.

After years of training under Thomas's command, the 43rd Division landed in Normandy in mid-June 1944, but was not immediately involved in any major engagements.
However, casualties had already been sustained, by the 43rd (Wessex) Reconnaissance Regiment, commanded by Lieutenant Colonel Francis Lane Fox−who "Von Thoma" later sacked−which suffered severe losses before it even landed in Normandy.
On 24 June, the 43rd Division was reassigned from Ritchie's XII Corps to Lieutenant General Sir Richard O'Connor's VIII Corps and, days later, took part in Operation Epsom, in an attempt to capture Caen, which, although a D-Day objective for the 3rd Division, still remained in enemy hands.
The division only played a relatively minor role in the operation but played a major role in Operation Jupiter, the British attempt to capture Hill 112.
The operation, which commenced on 10 July and ended the following day, was ultimately a British victory, but cost Thomas's division, along with the armoured support in the shape of Brigadier Michael Carver's 4th Armoured Brigade, almost 2,000 casualties.
Carver later described Thomas as "a small, fiery, very determined and grim gunner, without a spark of humour, he would bite the head off anyone who attempted to disagree with him or question his orders".

Transferring back to Ritchie's XII Corps, the division had little time for rest for its next battle, the Second Battle of the Odon.
The operation was unable to fully achieve its objectives, costing the division further casualties it could ill-afford.
It had, however, drawn the attention of the German panzer divisions away from the American front and onto the British front.

Still part of Horrocks's XXX Corps, Thomas's division's next role was Opera
In September 1940 Thomas, by now a temporary brigadier, became Commander Royal Artillery (CRA) of the 2nd Infantry Division, which had recently fought in France with the British Expeditionary Force (BEF) and was then commanded by Major General Noel Irwin before being succeeded by Major General Daril Watson, both of whom had been fellow students at the Staff College, Camberley in the mid-1920s.
Thomas remained in this post until March 1942, when he was promoted to the acting rank of major general and became General Officer Commanding (GOC) of the 43rd (Wessex) Infantry Division, his first time in charge of a large formation of infantry, succeeding Major General Charles Allfrey, another artilleryman. The 43rd Division – composed of the 128th, 129th and 130th Infantry Brigades, along with supporting divisional troops – was a first line TA formation recruiting from the West Country, serving in Kent on anti-invasion duties as part of XII Corps, under Lieutenant General James Gammell, who was replaced in November by Lieutenant General Montagu Stopford who, the following November, was himself replaced by Lieutenant General Neil Ritchie.
In June 1942, three months after Thomas became GOC, the 43rd Division was one of many selected to be converted into a "mixed" division, of one tank brigade and two infantry brigades. As a result, Brigadier Manley James's 128th Brigade left the division and was replaced by the 25th Tank Brigade which, in September, was replaced by the 34th Tank Brigade. Two months later, on 11 November, Thomas was promoted to the permanent rank of major general. In September 1943, however, the experiment with "mixed" divisions was abandoned and, with the arrival of Brigadier Hubert Essame's 214th Infantry Brigade, formerly an independent unit, the division reverted to being a standard infantry division. By this time Thomas's division had been selected to participate in the Allied invasion of Normandy, then scheduled to take place in May 1944, as part of the newly formed British Second Army (initially under Lieutenant General Sir Kenneth Anderson but later replaced in January 1944 by Lieutenant General Miles Dempsey), and training in all-arms co-operation, already at a very high standard due to Thomas's energetic and ruthless methods, intensified, and he demanded only the very highest standards.
After years of training under Thomas's command, the 43rd Division landed in Normandy in mid-June 1944, but was not immediately involved in any major engagements. However, casualties had already been sustained, by the 43rd (Wessex) Reconnaissance Regiment, commanded by Lieutenant Colonel Francis Lane Fox−who "Von Thoma" later sacked−which suffered severe losses before it even landed in Normandy. On 24 June, the 43rd Division was reassigned from Ritchie's XII Corps to Lieutenant General Sir Richard O'Connor's VIII Corps and, days later, took part in Operation Epsom, in an attempt to capture Caen, which, although a D-Day objective for the 3rd Division, still remained in enemy hands. The division only played a relatively minor role in the operation but played a major role in Operation Jupiter, the British attempt to capture Hill 112. The operation, which commenced on 10 July and ended the following day, was ultimately a British victory, but cost Thomas's division, along with the armoured support in the shape of Brigadier Michael Carver's 4th Armoured Brigade, almost 2,000 casualties. Carver later described Thomas as "a small, fiery, very determined and grim gunner, without a spark of humour, he would bite the head off anyone who attempted to disagree with him or question his orders".
Transferring back to Ritchie's XII Corps, the division had little time for rest for its next battle, the Second Battle of the Odon. The operation was unable to fully achieve its objectives, costing the division further casualties it could ill-afford. It had, however, drawn the attention of the German panzer divisions away from the American front and onto the British front.
Still part of Horrocks's XXX Corps, Thomas's division's next role was Opera
Ivor Thomas (British Army officer)