The origins of the Holt Tractor can be traced back to rural Lincolnshire, 1903. R. Hornsby & Sons, Grantham was the only entrant in the War Office tractor trial of 1903 and despite winning the £1,000 prize for completing the trial, furthered its abilities by converting it to a tracked vehicle in 1905. Although proving to be successful, the tractor was either too far ahead of its time or too cumbersome for the domestic market and when the opportunity arose, the patents were sold.

C.H. Holt & Co, founded in California in 1864 to build wooden wagon wheels and frames, had turned their attentions to agricultural machinery designed by Benjamin Holt, one of the founding brothers by the early 1900's. These huge machines were designed for the vast expanses of the Californian prairies, weighed 20 tons and were capable of hauling 50 ton loads.

They were, however, prone to sinking into the soft earth, even with the 6ft wide, 7ft diameter wheels that Holt used to combat sinking. In 1904, Holt developed the first track system, using Redwood for the tracks, which though more successful than wheels proved difficult to perfect.

At this time, Britain led the world with patenting various track laying designs and Holt travelled to England to study the English designs. Few of the designs worked in practice, except for the Hornsby and Holt bought the patents for the Hornsby tractor.

Holt continued to develop the Hornsby design and followed the Hornsby lead by replacing steam power with 4-cylinder petrol power in 1906. Although the tracks were kept very similar to the Hornsby, a major change was the addition of a wide, single wheel attached to a subframe at the front of the tractor. This was to aid stability and turning, which was achieved by declutching the tracks independently, allowing the tractor to skew round.

Despite a price tag of $5,500, the Holt tractor proved popular and by the outbreak of WW1, over 2000 had been built and sold. This popularity prompted Holt to seek markets further afield and agents were appointed worldwide, including England, France and Germany.

By 1915, the shortcomings of both horse and steamers in transporting heavy guns were apparent. Horses were too slow over the rough and usually muddy terrain and steamers alerted the enemy to their position by their smoke. The War Office purchased a Holt for trials at Aldershot and as a result it was chosen for use as a gun-tractor.

Although not as powerful as the 105hp Foster-Daimler, the 75hp Holt proved very capable of hauling 6-inch howitzers over the rough testing grounds at Aldershot. The ability to haul heavy loads over uneven ground was more important than speed. The Holt could only manage 2mph when towing and 4mph when travelling alone. Importantly, from the Army's viewpoint, was that Holts were readily available in numbers and initial orders were placed. By 1918, 2,100 Holts had been supplied to the War Office.

The ASC Depot Company, 52 MT Company, in Aldershot had incorporated a caterpillar section and was moved to Avonmouth in early 1915 to become the ASC Tractor Depot. The Holts were imported from the USA through Avonmouth and from here the ASC provided gun-tractors and men. From April 1915, 6, 8 and 9-inch howitzers were drawn by Holts. Holt drivers were also supplied to help develop the first tanks at Elvedon and to provide driver training and workshop support from 1916.

Workshop support for the Tank Corps extended to the battlefields of France. The tanks travelled by rail to the Somme, but the workshop travelled by road. The workshop comprised a trailer with lathes, drilling machines and spare wheels and a second trailer carrying a hydraulic press weighing 60 tons. The trailers were towed by two Holts from Le Havre to Bray-sur-Somme, departing two weeks ahead of the tanks.

The ASC 3rd Heavy Repair Shop at St Omer was the designated repair and servicing base for the Holts. The ability to rescue disabled tanks and lorries from soft ground made the Holt popular with the ASC Recovery crews who purloined their use at every available opportunity.

The full advantages of a track-laying vehicle appear not to have been realised until they were used in the quagmire of Northern France. The way these giant tractors crawled across the terrain soon earned them the nickname Caterpillar or 'Cat'.

Issued to the Royal Artillery for use as gun-tractors, alongside the American four-wheel drive Jeffrey and FWD lorries, the Holts were also pressed into service as supply trains. Generally this was hauling supplies and ammunition to the frontlines when the quagmire, trenches and barbed wire defeated the lorry and horse. The tracks of the Holt enabled it to cross trenches, barbed wire and shell-holes that wheeled vehicles were unable to.

When Britain and France sent six divisions each to the aid of the Italians in October 1917, it was the Holt tractor that proved essential in hauling the supplies and ammunition over the tortuous terrain with steep and twisting mountain roads. Following a route from Amiens, through Dijon, Lyons, Nice and eventually entering Italy through Savona, the journey was completed in just two weeks.

The performance of the Ford T in the desert conditions of Palestine is well known, but even they depended on wire netting used to create crude roads. Away from these netting roads, wheeled vehicles soon became bogged down in the sand. Here, the Holt changed its role from gun-tractor to supply train, usually towing two cargo trailers. These trailers were supplied by Holt, had tracks in place of wheels and 10-ton carrying capacity.

Whilst able to travel where wheeled vehicles could not, progress remained slow as the trailers were prone to shedding tracks when turning. Attempts were made with wheeled trailers, which became quickly bogged down and increased the risk of the tractor shedding its tracks, often resulting in the tractor rolling onto its side.

Two companies of Holt tractors were based at Basra, Mesopotamia with the dual role of gun-tractors and supply trains. The supply trains remained faithful to the idea of tracked trailers, although these were British built Fosters, who also built the Foster-Daimler tractor.

Originally conceived as an agricultural tractor, the Holt's significance to the military went far further than its role in the theatres of war. Lieutenant-Colonel Ernest Swinton, sent to France as an army war correspondent, was among the first to recognise the potential of a track-laying tractor.

By as early as October 1914, the difficulties faced by the terrain in France were apparent. Swinton saw that a tracked tractor had advantages in being able to traverse trenches and quagmire and put forward the idea of a bullet-proof, power-driven tracked vehicle capable of destroying enemy guns to Sir Maurice Hankey, Secretary of the Committee of Imperial Defence.

Initially finding no interest of support within the government, the idea eventually reached Winston Churchill, First Lord of the Admiralty. The original proposal to use the Holt as the basis for an armoured fighting vehicle was discarded in favour of developing the tank with Fosters & Sons whose managing director and designer was Sir William Tritton.

Holt components formed the basis of the German A7V tank and the inspiration behind Renault tanks. In American, two Holts were converted to tanks but then rejected after trials. Despite its cross-country abilities, it appears to have been too large and cumbersome for the relative agility required by the tank.

The Holt may not have been the first tank, but it appears to have inspired and heavily influenced the concept.

After the Armistice the Holt proved too slow to be transported under its own steam. The railways provided transport for tanks but the army looked to road transport for the Holt.

In 1919, AEC supplied the RASC with several articulated low-loaders. These were AEC Y types with chain driven rear axles. The chassis was shortened and equipped with a semi-trailer built by HC Bauley, designed to carry the Holt tractor.

This transporter was capable of carrying the Holt, but not the tanks which were some seven tons heavier. It was however the design that proved the concept of transporting tanks by road, so can lay claim to being the army's first tank transporter.

Hornsby were acquired by Ruston of Lincoln in September 1918, creating the firm of Ruston & Hornsby Ltd. In California, the two arch rivals in building tracked vehicles, Holt and C.L. Best merged in the early 1920's to form the world famous Caterpillar company.

From my article in Classic Military Vehicle, July 2007.