それと同時に、日本の勢力下にあった満洲への研究施設の設置も着手された
Shouldn't に be used here instead of へ? As far as I know, the function of へ is to denote the direction in which an action is taken, not a direction in which an action is taken.
に cannot be used because にの is an invalid combination. On the other hand, への is valid and compatible with 設置(する) probably because 設置 indicates something of direction (putting ... onto).
Note 満洲{へ,で,に}研究施設が設置される are possible. Then nominalizing them requires の after 満州+particle, so that they become 満洲{への,での}研究施設の設置.