History suggests that wars are harmful to stock markets (sometimes that’s a big understatement). Often, wars and major terrorist attacks send share prices plunging across the globe. After the US attacked Iran on Sunday, the FTSE 100 took two days to start sliding.

When stock prices fall suddenly, this can be a golden opportunity to buy into good businesses at fair prices. For example, here are two Footsie firms in which I’m thinking about increasing my family’s ownership.

FTSE falling

At its all-time high, the UK’s blue-chip index peaked at 10,934.94 points on Friday, 27 February. As I write on Tuesday afternoon, the index has dropped 3.5% and stands at 10,407.22, down 5.1% from its peak. This is hardly cause for panic, but military operations often prove tricky and last longer than expected. Hence, cautious investors may sell shares to avoid anticipated falls.

However, every stock sale includes a buyer and a seller, Thus, I often use lower prices to buy more discounted shares.

Dirty Diageo

Take global drinks Goliath Diageo (LSE: DGE), whose stock has been slumping since its record high at end-2021. At present, the share price is 1,577.5p, valuing this long-established British business at £35.1bn. That’s about three-fifths below its peak market value.

In common with other major suppliers of alcoholic drinks, Diageo’s sales are falling — especially in key regions such as the US and China. Hence, its shares have dived 27.2% over one year and crashed 46.4% over five years (excluding cash dividends).

Speaking of dividends, Diageo’s new CEO ‘Drastic’ Dave Lewis has more halved the dividend. His aim is to to cut Diageo’s debt pile and fund future growth. Thus, the trailing cash yield will likely be below 2% a year going forward.

That said, it’s not clear to me whether Diageo stock is a blow-out bargain or a value trap. I’d prefer to see signs of a turnaround in sales, profits, and cash flow before committing more money to this business. Therefore, I’ll hold fire for now.

Bunzl bounce back?

Bunzl (LSE: BNZL) is another British business with a global reach. It supplies various cleaning, safety, and hygiene products to organisations in North America, the UK and Ireland, Europe, and the rest of the world. Boosted by organic growth and repeated acquisitions, Bunzl boomed for almost two decades.

However, after the company warned of slowing growth on 16 April 2025, its shares crashed 25.6% that day. I swooped in, buying the stock for my family portfolio for 2,292p a share. As I write, the shares trade at 2,210p, so we’re down about 3.6% so far.

Then again, I have no interest in crystalising our paper loss. For me, this £7.2bn Footsie firm could be a classic ‘fallen angel’ that becomes a recovery play. Meanwhile, the shares are down 28.1% over one year, but up 1.5% over five years. So maybe 2024/25 price plunge was just a blip?

While we wait for Bunzl’s share price to recover, the stock pays us a decent dividend of 3.4% a year. What I’d like to see is a return to sales growth leading to higher earnings, but this could take time. But I’ll give Bunzl the benefit of the doubt — and I’ll consult with my co-manager (my wife) on whether we should buy more!