By spring 1915 the flow of recruits was dwindling. The government, torn when it came to the question of compulsory military service, tried a half-way house scheme.

Born in 1865, Edward Stanley became the 17th Lord Derby in 1908. He played a major part in raising volunteers, especially for the King's (Liverpool) Regiment, before being appointed Director-General of Recruiting in October 1915.

In spring 1915, enlistments averaged 100,000 men per month, but this could not be sustained. The upper age limit was raised from 38 to 40 in May 1915 in an effort to keep the numbers up, but it had become clear that voluntary recruitment was not going to provide the numbers of men required. The government passed the National Registration Act on 15 July 1915 as a step towards stimulating recruitment and to discover how many men between the ages of 15 and 65 were engaged in each trade. All those in this age range who were not already in the military were obliged to register, giving details of their employment details. The results of this census became available by mid-September 1915: it showed there were almost 5 million males of military age who were not in the forces, of which 1.6m were in the "starred" (protected, high skill) jobs. On 11 October 1915, Lord Derby was appointed Director-General of Recruiting. He brought forward a programme five days later, always called the Derby Scheme, for raising the numbers. Men aged 18 to 40 were told that they could continue to enlist voluntarily, or attest with an obligation to come if called up. The War Office notified the public that voluntary enlistment would soon cease and that the last day of registration would be 15 December 1915. The men who registered under the Derby Scheme were classified into married and single, and into 23 groups according to their age. Group 1 was for single 18 year-olds, then by year up to Group 23 for single 40's; then Group 24 was for married 18 year-olds up to Group 46 for married 40's. At the same time, a war pension was introduced, to help entice men concerned about supporting their dependents given the all too-obvious chance that they may not survive.

Men who attested under the Derby Scheme were sent back to their homes and jobs until they were called up. They wore a grey armband with a red crown as a sign that they had so volunteered.

215,000 men enlisted while the scheme was on and another 2,185,000 attested for later enlistment - but 38% of single men and 54% of marrieds who were not in "starred" jobs had still avoided this form of recruitment. Their reticence did much to hasten a move to full conscription. Voluntary attestation reopened on 10 January 1916, while the government considered the position.

Call up under the Derby Scheme began: Groups 2 to 5 were called up in the last two weeks of January 1916, and Groups 6 to 13 in February. The last single groups other than the 18 year-olds were called up in March. This last batch were called up in parallel to the first men to be summoned under conscription under the Military Service Act. The recruits were not necessarily posted to their local regiments and from this time one it is not wise to assume that a man would go into his local regiment.