Nish ably goes through the failure in negotiations that led up to the Russo-Japanese war. He apparently understands at least 3 languages (not just English, but also Russian and Japanese), and combs through a wide array of source material to trace the origins of this war. The lead-up to war is worth studying in its own right, but it also sheds light on parallel decision making in Russia in 1914 and Japan in 1941.
In a nutshell, Russia had built a railway in Manchuria that it sought to protect. Japan had a colony of sorts in Korea. Throughout this period, Japan tried to negotiate with Russia about a treaty that would define spheres of influence. Japan, which started the war, wanted to preserve its position in Korea, and it saw Russia's presence in Manchuria as threatening to that. Japan was on the diplomatic side of the Open-Door powers (UK and USA) who wanted Russia completely out of China. Japan outmaneuvered Russia diplomatically by gaining an alliance with the UK; this allowed Japan to act with some freedom later, as she didn't have to worry about a Western alliance similar to the one that undercut her in 1895.
For its part, Japan tried numerous times to negotiate with Russia. It seems that there could have been a deal struck on the basis of trading Korea for Manchuria, in a sense; Japan preserves dominance in Korea, while Russia does so in Manchuria. However, Russia never saw Manchuria as being on the table; Russia consistently maintained that Russian presence there was a bilateral Chinese-Russian matter.
Russian policy was incoherent, as opinion was divided among ministers, or among those in St. Petersburg vs those in Port Arthur. Exacerbating matters, a Russian connected to the court opened a timber company on the Yalu river. This one issue seems to have reinforced fears in Japan about Russian incursions from Manchuria into Korea.
Making matters even worse, the Tsar often had to push off making a decision due to various personal reasons (vacationing in Crimea, illness of the Tsarina, and so on). Japan read these delays as intentional prevarication, and in some sense that's true, as Russia had no sense of urgency about resolving the issue and, quite frankly, never took the threat of Japanese capacity or intentions for war seriously. Russian reactions during this period have a somnambulatory quality that reminded me of Christopher Clark's The Sleepwalkers, a certain disconnectedness from events that seems peculiar to Nicholas II, right up to his last days.
Meanwhile, I was reminded of the start of the later Pacific War as I read about the Japanese side. There were factions for and against the war, chief of which were the army (pro) and navy (con). Japan broke off diplomatic negotiations, but didn't declare war before the shooting started, a murky situation that didn't seem to harm it here, but the parallels with 1941 are clear. It's perhaps no wonder that Japan, which had brought one sleeping giant to terms, thought it could do so again.
Nish discusses whether the war was preventable or not, and his conclusion is that it wasn't. Based on what he presents, I disagree. It seems that if Russia had withdrawn from Manchuria, and signed some sort of treaty with Japan over Korea, things could have been resolved adequately, at least in the short term. My conclusion is that Russia could have avoided what followed by negotiating with Japan much sooner. Ironically, though, it may be that Manchuria was simply not so important to the Russians as it was to the Japanese.
As for the other side, I'm not sure what was at stake for Japan in going to war, but obviously they felt their interests and self-respect sufficiently threatened and acted accordingly. One wonders whether they should have simply followed Russia's course and let things continue as they were. But they may have felt (as they would in 1941) that their enemy would only get stronger and more firmly ensconced as time went on; therefore, there's no better time to strike than now. In any case, the Japanese public was for it, based on Nish's readings of newspapers of the day.
Readers can draw their own conclusions and parallels in this excellent study. Nish's prose is somewhat stodgy and a slog to get through -- it took me much longer than I thought it would to get through the 250 main pages of narrative. However, his command of the sources (Russian and Japanese), and his analysis of them, provide much to consider.