  Most back hole and neutron star progenitors are found in triples or higher
multiplicity systems. Here, we present a new triple stellar evolution code,
${\tt TSE}$, which simultaneously takes into account the physics of the stars
and their gravitational interaction. ${\tt TSE}$ is used to simulate the
evolution of massive stellar triples in the galactic field from the
zero-age-main-sequence until they form compact objects. To this end, we
implement initial conditions that incorporate the observed high correlation
between the orbital parameters of early-type stars. We show that the
interaction with a tertiary companion can significantly impact the evolution of
the inner binary. High eccentricities can be induced by the third-body
dynamical effects, leading to a Roche lobe overflow or even to a stellar merger
from initial binary separations $~10^3$ - $10^5\,\rm R_\odot$. In $\sim5\,\%$
of the systems the tertiary companion itself fills its Roche lobe, while $\sim
10\,\%$ of all systems become dynamically unstable. We find that between
$0.3\%$ and $5\%$ of systems form a stable triple with an inner compact object
binary, where the exact fraction depends on metallicity and the natal kick
prescription. The vast majority of these triples are binary black holes with
black hole companions. We find no binary neutron star in any surviving triple,
unless zero natal kicks are assumed. About half of all black hole binaries
formed in our models are in triples, where in the majority the tertiary black
hole is able to perturb their long-term evolution. Our results show that triple
interactions are key to a full understanding of massive star evolution and
compact object binary formation.

Solar and Stellar Astrophysics;High Energy Astrophysical Phenomena