21 SAS Reserve Selection Process: Five Published Stages (2026)

By Deepak Shukla · Historical account and source-led commentary · Updated 7 November 2026

The British Army's SAS Reserve recruiting page describes five formal stages: a briefing course, aptitude, operating procedures and tactics, surveillance/reconnaissance with SERE, then continuation training. For someone applying from civilian life, the crucial detail comes before that list: basic Army training and experience. I learned how easy it is to confuse those early steps with the selection stages themselves when I applied in 2014. Here is the published pathway, in order.

The stage most internet guides skip: becoming prepared as a soldier

For an applicant entering without prior service, the official Army role description says that basic military training, initial trade training and experience come before attempting selection. This matters because an Army assessment weekend, a recruit-training course and Special Forces selection are not interchangeable events. My 2015 diary about ATC Pirbright is valuable precisely as a description of an early stage; it should not be represented as an account of completing selection.

Stage one: the briefing course

The Army Jobs page calls this a six-day briefing and assessment. It is intended both to explain what lies ahead and to assess an applicant's suitability for progression. An applicant should treat current timings, fitness measures and entry conditions as information to obtain from the recruiting team. My own notes were written years before the present description, so I do not try to map every day of my historical application onto today's published timetable.

Stage two: aptitude

The official public summary describes a continuous period of assessed physical and mental resilience, including progressive timed marches. Its importance is obvious without reproducing test timings or tactical details from unofficial forums: the Army is assessing suitability for a demanding military role, not simply a runner's personal best. Do not use old race reports as a proxy for a military assessment.

Stage three: standard operating procedures and tactics

After aptitude, the Army's published description identifies a further course requiring people to learn and apply military skills under pressure. It is enough for a public guide to name this part of the pathway and point to the official source. Describing technical content I never trained in would add false authority and do applicants no favour.

Stage four: reconnaissance, SERE and the different official labels

Army Jobs calls stage four surveillance, reconnaissance and SERE; the British Army 21/23 SAS page titles the corresponding phase Special Operations Procedures & Tactics - 2, then also names those areas. That difference comes from the two official pages. I have no firsthand basis for describing the internal training or the arrangements for a particular intake.

Stage five: continuation or mandatory training

Army Jobs calls the final published stage Continuation Training. The British Army 21/23 SAS page uses Mandatory Training and describes further work before full deployability. Neither label describes my own experience. Completing early Alpha or Bravo training does not put somebody at the end of selection; I stopped before the formal course in June 2016.

How long does all this take?

A useful question is how much time to allow for initial Army training, applications, preparation, selection windows and ongoing service—not how quickly somebody can cram through a fixed sequence. Army Jobs includes durations for some stages; these can change and do not cover the entire journey. The October 2025 Soldier recruitment feature discusses a sustained selection commitment. Ask the unit for your pathway and your current availability rather than planning around a number extracted from a blog.

Read the experience alongside the requirements

My application began with a late-night internet search. The Pirbright diary tells the story of an early Army assessment; the longer chronology covers Alpha, Bravo, preparation evenings and why I eventually stopped. These are human stories rather than manuals for the five formal stages listed here. Read them for the experience, and rely on the current Army links for the rules.

Why a Pirbright assessment or Alpha/Bravo is not SAS selection

An ordinary Army entry assessment and Alpha or Bravo Army preparation can happen before a later SAS Reserve selection course. My original diaries are from that preparatory period. The 21 SAS-linked weekend where our performance was assessed was real, but I never reached the later formal selection course. This matters if you are using an applicant's experience to understand what a public stage name means.

Does the Reserve follow the same selection as the Regular SAS?

The Army describes UKSF pathways with shared elements, but a broad web summary should not promise identical entry, timetables or service arrangements for 21, 23 and 22 SAS. Compare the Army's current official descriptions and ask recruiting for the applicable route. A 2015 applicant's anecdotes are not an authoritative comparison of present-day courses.

21 SAS reserve selection process: where each stage fits