I have been trying to find an accurate representation of what regions in china were owned by Japan before and at the start of the second sino-japanese war. I have found some sources stating it was only manchuria that was occupied before the marco polo bridge incident (like i believed) however some sources state they owned land as inland as Beijing and half the chinese coast. Does anyone have accurate maps describing the progression of Japan's occupation of China?
Well Japan certainly didn’t hold half of China’s coast before the 1937 invasion, though it did have a presence at various points and its control through intermediaries extended to within a dozen miles of Beijing.
Japan’s army in the Guandong leased territory and the South Manchuria Railway zone had taken over Manchuria, easternmost inner Mongolia and Rehe (then commonly known outside China as Jehol) in 1931-33, subsequently assembling them into the puppet empire of Manchuguo, though a 1932 attack on Chinese forces at Shanghai failed to capture the city.
Under renewed Japanese pressure in 1935 the Chinese government (based in Nanjing) renounced rule in Hebei (including Beijing and Tianjin) and most of Chahar, setting up instead a sympathetic “Hebei and Chahar political council” to administer the region in opposition to a pro-Japanese “autonomous government” in northeastern Hebei, though Japanese-backed Mongol forces took over northern Chahar.
Elsewhere, Japan had a garrison at Tianjin under the 1901 Boxer Protocol for use in guarding legations and Japanese interests, and concessions (urban quarters under foreign control) there and in the cities of Suzhou, Hangzhou, Hankou, Shashi and Xiamen, along with a share (and 2,000 troops) in the Shanghai international concession.
I’ve seen a map showing Hebei, Shandong, Shanxi, Chahar and Suiyuan as a “Japanese puppet state” from 1935, which you may have in mind: in fact that status then only applied to northeastern Hebei and most of Chahar, a small part of the five provinces concerned: the provincial governors of Shandong and Shanxi paid little heed to Nanjing but still less to Japan, while forces loyal to Nanjing fought off a 1936 invasion of Suiyuan by Japanese proxies.
Another version of the map shows the five provinces as part (from 1934!) of the Mengjiang inner Mongolian state which wasn’t proclaimed until 1939, even then incorporating only a northern strip of Shanxi alongside Chahar and Suiyuan, which fell only in the early stages of the 1937 war.
It’s surprisingly difficult to find a good map of the situation around early 1937: of the various ones in Google images I think this comes closest, though it's worth noting that the label “Inner Mongolia” here represents the Japanese puppet state in Chahar rather than the wider region.