  The International Linear Collider (ILC) is now under consideration as the
next global project in particle physics. In this report, we review of all
aspects of the ILC program: the physics motivation, the accelerator design, the
run plan, the proposed detectors, the experimental measurements on the Higgs
boson, the top quark, the couplings of the W and Z bosons, and searches for new
particles. We review the important role that polarized beams play in the ILC
program. The first stage of the ILC is planned to be a Higgs factory at 250 GeV
in the centre of mass. Energy upgrades can naturally be implemented based on
the concept of a linear collider. We discuss in detail the ILC program of Higgs
boson measurements and the expected precision in the determination of Higgs
couplings. We compare the ILC capabilities to those of the HL-LHC and to those
of other proposed e+e- Higgs factories. We emphasize throughout that the
readiness of the accelerator and the estimates of ILC performance are based on
detailed simulations backed by extensive RandD and, for the accelerator
technology, operational experience.
