Today in Postal History

This worn cover  was mailed from Knutsford about 20 km southwest of Manchester.
It was cancelled with a duplex cancel with an oval 425 killer and a Knutsford CDS.
It was addressed to a member of the Royal Artillery stationed in Sitapur, India.
Sitapur is about 380 km south southeast of Delhi.
Routing Via Brindisi was requested.

The next marking is a Sea Post Office on July 25.
I believe this would have been either after passing through Brindisi or at a transfer at Suez.
Anyone?

There is a small illegible circular stamp near the right center on the back.
Is this a Brindisi mark?

The letter arrived in Sitapur on August 8 where it was readdressed to Lundi Kotal
(now Landi Kotal) on the present day Afghan border about 40 km west northwest of Peshawar.
The cover was given an arrival CDS, a departure CDS,
and a boxed REDIRECTED handstamp in Sitapur.

It arrived in Lundi Kotal on August 12.

The letter is franked with a wing copy of the 1874
6d. gray perf 12 Victoria (possibly 1878 plate 16 SG 147).

The addressee was deployed with British troops fighting the Second Afghan War.
The letter probably traveled for some time in the soldier's gear leading to the wrinkling.
The letter arrived after a treaty had been signed presumably ending the war.
However, the British Viceroy in Kabul was assassinated in September and it all started over again.