The phrase "a string of defence" is correct and usable in written English.
It can be used when referring to a series of arguments or actions taken to protect or justify something.
Example: "In her speech, she presented a string of defence for her controversial decision, hoping to sway public opinion."
Alternatives: "a series of justifications" or "a chain of arguments".
Rounding a bend in the lane the approach to the village is watched over by the earthworks of a Norman castle motte, one of a string of long-gone defences along the rim of the Dale.
Strachan's side had to survive a first-half battering as the Czech Republic fought ferociously with pace and power in their bid to draw level but the goalkeeper Allan McGregor was in inspired form, making a string of saves, and his defence helped out after the break to hold on for the morale-boosting win.
While successive national defence authorisation acts have indeed imposed a string of conditions on the US secretary of defence over any releases – a so-called "certification" process – there's also a waiver system for some of the conditions.
She became Brazil's youngest ever female senator and won a string of international awards for her defence of the environment and its people.
The Australian also rallied behind Lachlan Murdoch, interviewing "a group of high-profile businessmen who have worked closely with Mr Murdoch [who] leapt to his defence, citing a string of successful business ventures that prove his strong leadership credentials and a talent for identifying investment opportunities".
An unusual feature of Montreal's defence was a string of 30 outlying forts to protect against the constant Iroquois threat to the expansion of French settlements.
The protesters, who have blockaded the entrance with a string of tents, identify themselves as self-defence forces of Donbass, the coalmining and metalworking region with strong historical and economical ties to Russia.
This is a company that has been picking up a string of contract wins in the education and defence sectors.
In the win over West Ham, he made a string of important saves after momentary lapses in defence and claimed a clean sheet with an excellent save.
There were a string of central defenders who played the ball out of defence before Ferdinand and who frankly were better players.
