Japan's threat to the Philippines in 1939

How much of a threat would Japan pose to the Philippines in this scenario?

A limited one at first: Japan lacks the prepared troops, logistics, and surprise that enabled its 1941 offensive, while the Philippines would have time to mobilize and strengthen its defenses.

The January 1939 starting point denies Japan both the Pearl Harbor blow against the US Pacific Fleet and the carefully positioned invasion force used in the historical campaign. Japanese troops, shipping, fuel, and air support are not yet assembled for the coordinated offensive of December 1941. Any later attack would meet an alerted and increasingly armed Philippines rather than a defender caught by strategic surprise. Time also gives the local command an opportunity to mobilize and correct weaknesses before Japanese forces can be repositioned for an invasion.