  We analyse the gas content evolution of infalling haloes in cluster
environments from THE THREE HUNDRED project, a collection of 324 numerically
modelled galaxy clusters. The haloes in our sample were selected within
$5R_{200}$ of the main cluster halo at $z=0$ and have total halo mass
$M_{200}\geq10^{11} h^{-1} M_{\odot}$. We track their main progenitors and
study their gas evolution since their crossing into the infall region, which we
define as $1-4R_{200}$. Studying the radial trends of our populations using
both the full phase space information and a line-of-sight projection, we
confirm the Arthur et al. (2019) result and identify a characteristic radius
around $1.7R_{200}$ in 3D and at $R_{200}$ in projection at which infalling
haloes lose nearly all of the gas prior their infall. Splitting the trends by
subhalo status we show that subhaloes residing in group-mass and low-mass host
haloes in the infall region follow similar radial gas-loss trends as their
hosts, whereas subhaloes of cluster-mass host haloes are stripped of their gas
much further out. Our results show that infalling objects suffer significant
gaseous disruption that correlates with time-since-infall, cluster-centric
distance and host mass, and that the gaseous disruption they experience is a
combination of subhalo pre-processing and object gas depletion at a radius
which behaves like an accretion shock.
