  The CALICE collaboration is developing highly granular electromagnetic and
hadronic calorimeters for detectors at future energy frontier electron-positron
colliders. After successful tests of a physics prototype, a technological
prototype of the Analog Hadron Calorimeter has been built, based on a design
and construction techniques scalable to a collider detector. The prototype
consists of a steel absorber structure and active layers of small scintillator
tiles that are individually read out by directly coupled SiPMs. Each layer has
an active area of $72 \times 72\,{\rm cm}^{2}$ and a tile size of $3 \times
3\,{\rm cm}^{2}$. With $38$ active layers, the prototype has nearly $22,000$
readout channels, and its total thickness amounts to $4.4$ nuclear interaction
lengths. The dedicated readout electronics provide time stamping of each hit
with an expected resolution of about $1\,{\rm ns}$. The prototype was
constructed in 2017 and commissioned in beam tests at DESY. It recorded muons,
hadron showers and electron showers at different energies in test beams at CERN
in 2018. In this paper, the design of the prototype, its construction and
commissioning are described. The methods used to calibrate the detector are
detailed, and the performance achieved in terms of uniformity and stability is
presented.
