The people of Novgorod were evidently obsessive record-keepers, and 
_The Chronicle of Novgorod_ details the important events in the city
in a given year. I list the entries from 1250 AD until 1255 AD, in
order to give context to the Saga. In the case of the longer entries,
I have abridged things to the essential details. I have also added
clarifications in brackets, where necessary.

1250:  Knyaz (Prince) Alexander returned from the Horde, and there was
       great joy in Novgorod. [He had left in 1246.]

1251:  The Metropolitan Kyuril and the Bishop of Rostov, also named
       Kyuril, came to Novgorod, and established Dalmat as Vladyka (Bishop)
       of Novgorod. Heavy rains came the same year and took away all the
       ploughed field and crops and hay; and the water carried away the
       large bridge over the Volkhov, and in the autumn a frost struck
       the crops, but a remnant was preserved.

1252:  Slavno was burnt down from St. Ilya up to Nutno Street.

1253:  The Lithuanians ravaged the district of Novgorod and went off with
       the captives, and the men of Novgorod with Knyaz Vasili overtook 
       them at Toropets, and so Christian blood was avenged on them. And
       they defeated them and took back the captives from them, and returned
       well to Novgorod.  [More battle details, from further-off areas,
       are also reported.]

1254:  It was well with the Christians.

1255:  [There's a bit of a brief civil insurgence between Alexander and
       his son Vasili, and some other people. As a result, the old
       posadnik, Anani, is removed from his office, though the circumstances
       are a bit complex.] ... there was not great shedding of Christian
       blood. And Knyaz Alexander took his seat upon the throne. And the
       same year they gave the posadnik-ship to Mikhalko Stepanovich.

The period which follows this is one of several civil insurrections,
involving Alexander, his son, and various other angry parties. This
is the period in which the characters will be participating, and it's
quite possible some of the outcomes will be different, so this is where
my quoting ends; those interested in more can go to their local library.