An implantation instrument for an expandable intervertebral fusion implant that includes a base piece and a cover piece that are configured to bear on a facing end plate of one of two adjacent vertebrae, the cover piece being adjustable in height with respect to the base piece, and a ratchet mechanism being provided between the base piece and the cover piece to effect a stepped adjustment of height and secure an adopted height again reversal, the implantation instrument being configured for expanding the intervertebral fusion implant and comprising a force measurer that interacts with a displacement measurer to indicate an expansion attained by a particular actuating force.