select *
from (
  select b.name, 
    convert(datetime, dateadd(day, 1-day(b.date), b.date), 20) as dt1,
    convert(datetime, dateadd(month, 1, dateadd(day, 1-day(b.date),b.date)) - 1, 20) as dt2
  from battles b
) tt
----
Guadalcanal	1942-11-01 00:00:00.000	1942-11-30 00:00:00.000
North Atlantic	1941-05-01 00:00:00.000	1941-05-31 00:00:00.000
North Cape	1943-12-01 00:00:00.000	1943-12-31 00:00:00.000
Surigao Strait	1944-10-01 00:00:00.000	1944-10-31 00:00:00.000
---------
select tt.name, left(tt.dt1, charindex(' ', tt.dt1))
from (
  select b.name, 
    convert(datetime, dateadd(day, 1-day(b.date), b.date), 20) as dt1,
    convert(datetime, dateadd(month, 1, dateadd(day, 1-day(b.date),b.date)) - 1, 20) as dt2
  from battles b
) tt
----
Guadalcanal	Nov 
North Atlantic	May 
North Cape	Dec 
Surigao Strait	Oct