What was the ethnic makeup of Lenin's bodyguards during the assassination attempt?

The theory about Chinese bodyguards of Lenin appears to be bogus. As far as I know, it first surfaced in the 1950s during the period of "great friendship" between the Soviet and Chinese people (only to disappear in 1960s, with deterioration of the relations between the two countries). It again resurfaced few years ago in the form of Sino-Russian made-for-TV documentaries. It is true, however, that there were Chinese regiments fighting on the side of the Red Army during Russian Civil War.

As a general rule, Soviet sources should be treated very cautiously, but here is what I can say on the basis of what is available.

1. Lenin did not like the idea of bodyguards. His first de-facto bodyguard was his personal driver, Степан Казимирович Гиль, Stepan Gil'. He left a set of memoirs,

Шесть лет с В. И. Лениным. Воспоминания личного шофера Владимира Ильича Ленина.

"6 years with Lenin. Memoirs of Lenin's personal driver." Moscow, 1957.

Most importantly, he was present during Kaplan's assassination attempt in August of 1918; Gil' describes the event in his memoirs. Judging by the description, he was the only Lenin's bodyguard present at the event. Here is his description of Lenin's attitude to his security prior to the assassination attempt:

Жизнь Владимира Ильича по нескольку раз в день подвергалась смертельной опасности. Эта опасность усугублялась еще тем, что Владимир Ильич категорически отказывался от какой бы то ни было охраны. При себе он никогда не носил оружия (если не считать крошечного браунинга, из которого он ни разу не стрелял) и просил меня также не вооружаться. Однажды, увидев у меня на поясе наган в кобуре, он ласково, но достаточно решительно сказал:

— К чему вам эта штука, товарищ Гиль? Уберите-ка ее подальше!

Однако револьвер я продолжал носить при себе, хотя тщательно скрывал его от Владимира Ильича. Наган находился у меня под рубашкой за поясом, без кобуры.

The life of Vladimir Ilyich [Lenin] was constantly in a mortal danger. This danger was further aggravated by the fact that Vladimir Ilyich absolutely refused any protection. He never carried any weapons with him (except for a tiny Browning, from which he had never fired) and asked me not to arm myself either. Once, when he saw a gun in a holster on my belt, he affectionately but decisively said:

“Why do you need this thing, Comrade Gil?” Take her away!

However, I continued to carry the revolver with me, although I carefully concealed it from Vladimir Ilyich. The gun was under my shirt and belt, without a holster.

2. The general security in Lenin's official residence (first, the Smol'ny Palace in St. Petersburg - Petrograd, then in Kremlin, in Moscow) was supervised by Павел Дмитриевич Мальков, Pavel Mal'kov, the "commandant" of Smolny and, then, Kremlin. He also left memoirs:

   Мальков П. Д. Записки коменданта Кремля. — М.: Воениздат, 1987., "Memoirs of the Kremlin Commandant," first published in 1960s.

Neither Gil' nor Mal'kov mention any Chinese bodyguards. However:

3. Latvian_Riflemen are frequently mentioned as guarding Smol'ny and then Kremlin. See for instance Mal'kov's memoirs and the linked Russian Wikipedia page. (The English-language mirror is much less detailed.)

How well did they speak Russian? I think, it is safe to conjecture that their Russian was accented but pretty good: since Latvia was a part of the Russian Empire for about two centuries (in fact, it was conquered by Russia under Ivan IV in the late 16th century and then changed hands several times). Gil', judging by his patronymics, was of Polish descent, while Mal'kov was likely ethnically Russian. I am sure, one can investigate this much further and maybe find that Mal'kov's ancestors were in fact Tatars or even Mongols, so, possibly, Chinese, since Mongol empire at its peak included much of Russia and China.

Regarding security in Smol'ny and Kremlin: According to Mal'kov's book, until September 1918 it was done by Latvian Riflemen, who in September 1918 were replaced ("according to their own wishes") by cadets of the 1st Machine-gun training school in Moscow. [Personally, I do not believe the explanation; my guess is that this decision was influenced by the assassination attempt and by "Lokhart's plot."]

Edit. Here is a link to a book written by Li Fuqing (available on Amazon):

Diary of a Lenin's Chinese guard Li Fuqing who visited the Soviet Union (Chinese Edition)

Li Fuqing claimed to have served as one of the 70 Chinese soldiers, guarding Lenin's office in Smonl'y and Kremlin in from January 1918 through Spring of 1919. See also here.