 Special reservists were permitted to agree to serve for an indefinite period without discharge, and could agree in writing to be liable for callout without a proclamation or order of Parliament.No more than four thousand men could be liable under this latter provision at any one time, and the power was not to be exercised except for overseas service when "warlike operations are in preparation or in progress".The Reserve Forces and Militia Act 1898 was extended to allow up to six thousand men in total to be liable for callout without proclamation, and for the period of their liability to be up to two years.