user: Question: How many figures are named for security forces in 1998?
Columns: ['Period', 'Civilians', 'Security forces', 'Insurgents', 'Total per period']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1996.0, 'N/A', 'N/A', 'N/A', 156.0]
SQL:

assistant: SELECT "Security forces" FROM "Table" WHERE "Period" = 1998.0;